MCP2515-E/PRB2 - Microchip Technology

MCP2515

Features

• Implements CAN V2.0B at 1 Mb/s:

- 0 – 8 byte length in the data field

- Standard and extended data and remote

frames

• Receive buffers, masks and filters:

- Two receive buffers with prioritized message

storage

- Six 29-bit filters

- Two 29-bit masks

• Data byte filtering on the first two data bytes

(applies to standard data frames)

• Three transmit buffers with prioritizaton and abort

features

• High-speed SPI Interface (10 MHz):

- SPI modes 0,0 an d 1,1

• One-shot mode ensures message transmission is

attempted only one time

• Clock out pin with programmable prescaler:

- Can be used as a clock source for other

device(s)

• Start-of-Frame (SOF) signal is available for

monitoring the SOF signal:

- Can be used for time-slot-based protocols

and/or bus diagnostics to detect early bus

degredation

• Interrupt output pin with selectable enables

• Buffer Full output pins configurable as:

- Interrupt output for each receive buffer

- General purpose output

• Request-to-Send (RTS) input pins individually

configurable as:

- Control pins to request transmission for each

transmit buffer

- General purpose inputs

• Low-power CMOS technology:

- Operates from 2.7V – 5.5V

- 5 mA active current (typical)

- 1 µA standby current (typical) (Sleep mode)

• Temperature ranges supported:

- Industrial (I): -40°C to +85°C

- Extended (E): -40°C to +125°C

Description

Microchip Technology’s MCP2515 is a stand-alone

Controller Area Network (CAN) controller that imple-

ments the CAN specification, version 2.0B. It is capable

of transmitting and receiving both standard and

extended data and remote frames. The MCP2515 has

two acceptance masks and six acceptance filters that

are used to filter out unwanted messages, thereby

reducing the host MCUs overhead. The MCP2515

interfaces with microcontrollers (MCUs) via an industry

standard Serial Peripheral Interface (SPI).

Package Types

TXCAN

RXCAN

VDD

RESET

MCP2515

SCK

INT

RX0BF

RX1BF

OSC2

OSC1

CLKOUT/SOF

TX2RTS

Vss 9

TX0RTS

TX1RTS

MCP2515

TXCAN

RXCAN

TX0RTS

OSC1

CLKOUT/SOF

OSC2

VDD

RESET

SCK

INT

RX0BF

RX1BF

VSS

TX1RTS

TX2RTS

NC NC

18-Lead PDIP/SOIC

20-LEAD TSSOP

Stand-Alone CAN Controller With SPI Interface

MCP2515

NOTES:

MCP2515

1.0 DEVICE OVERVIEW

The MCP2515 is a stand-alone CAN controller

developed to simplify applications that require

interfacing with a CAN bus. A simple block diagram of

the MCP2515 is shown in Figure 1-1. The device

consists of three main blocks:

1. The CAN module, which includes the CAN

protocol engine, masks, filters, transmit and

receive buffers.

2. The control logic and registers that a re used to

configure the device and its operation.

3. The SPI protocol block.

An example system implementation using the device is

shown in Figure 1-2.

1.1 CAN Module

The CAN module handles all functions for receiving

and transmitting messages on the CAN bus. Messages

are transmitted by first loading the appropriate

message buffer and control registers. Transmission is

initiated by using control register bits via the SPI

interface or by using the transmit enable pins. Status

and errors can be checked by rea ding the appropri ate

registers. Any message detected on the CAN bus is

checked for errors and then matched against the user-

defined filters to see if it should be moved into one of

the two receive buffers.

1.2 Control Logic

The control logic block controls the setup and operation

of the MCP2515 by interfacing to the other blocks in

order to pass information and control.

Interrupt pins are provided to allow greater system

flexibility. There is one multi-purpose interrupt pin (as

well as specific interrupt pins) for each of the receive

registers that can be used to indicate a valid message

has been received and loaded into one of the receive

buffers. Use of the specific interrupt pins is optional.

The general purpose interrupt pin, as well as status

registers (accessed via the SPI interface), can also be

used to determine when a valid message has been

received.

Additionally, there are three pins available to initiate

immediate transmission of a message that has been

loaded into one o f the three transmit registers. Use of

these pins is optional, as initiating message

transmissions can also be accomplished by utilizing

control registers, accessed via the SPI interfa ce.

1.3 SPI Protocol Block

The MCU interfaces to the device via the SPI interface.

Writing to, and reading from, all registers is

accomplished using standard SPI read and write

commands, in addition to specialized SPI commands.

FIGURE 1-1: BLOCK DIAGRAM

SPI

Interface

Logic SPI

Bus

INT

SCK

CAN

Protocol

Engine

RXCAN

TXCAN

Control Logic

RX0BF

RX1BF

TX0RTS

TX1RTS

TX2RTS

TX and RX Buffers

Masks and Filters

CAN Module

RESET

Timing

Generation

OSC1

OSC2

CLKOUT

Control

and

Interrupt

Registers

MCP2515

FIGURE 1-2: EXAMPLE SYSTEM IMPLEMENTATION

TABLE 1-1: PINOUT DESCRIPTION

Name PDIP/SOIC

Pin # TSSOP

Pin # I/O/P

Type Description Alternate Pin Function

TXCAN 1 1 O Transmit output pin to CAN bus —

RXCAN 2 2 I Receive input pin from CAN bus —

CLKOUT 3 3 O Clock ou tput pin with programmable

prescaler Start-of-Frame signal

TX0RTS 4 4 I T ransmit buf fer TXB0 request-to-send.

100 kΩ internal pull-up to VDD General purpose digital input.

100 kΩ internal pull-up to VDD

TX1RTS 5 5 I T ransmit buf fer TXB1 request-to-send.

100 kΩ internal pull-up to VDD General purpose digital input.

100 kΩ internal pull-up to VDD

TX2RTS 6 7 I T ransmit buf fer TXB2 request-to-send.

100 kΩ internal pull-up to VDD General purpose digital input.

100 kΩ internal pull-up to VDD

OSC2 7 8 O Oscillator output —

OSC1 8 9 I Oscillator input External clock input

VSS 9 10 P Ground reference for logic and I/O pins —

RX1BF 10 11 O Receive buffer RXB1 interrupt pin or

general purpose digital output General purpose digital output

RX0BF 11 12 O Receive buffer RXB0 interrupt pin or

general purpose digital output General purpose digital output

INT 12 13 O Int errupt output pin —

SCK 13 14 I Clock input pi n for SPI in te rf ace —

SI 14 16 I Data input pin for SPI interface —

SO 15 17 O Data output pin for SPI interface —

CS 16 18 I Chip select input pin for SPI interface —

RESET 17 19 I Activ e lo w de v i c e re set input —

VDD 18 20 P Positive supply for logic and I/O pins —

NC — 6,15 — No internal connection

Note: Type Identification: I = Input; O = Output; P = Power

Node

Controller

MCP2515

XCVR

SPI

TX RX

CANH

CANL

Node

Controller

MCP2515

XCVR

SPI

TX RX

Node

Controller

MCP2515

XCVR

SPI

TX RX

MCP2515

1.4 Transmit/Receive Buffers/Masks/

Filters

The MCP2515 has three transmit and two receive

buffers, two acceptance masks (one for each receive

buffer) and a total of six acceptance filters. Figure 1-3

shows a block diagram of these buffers and their

connection to the protocol engine.

FIGURE 1-3: CAN BUFFERS AND PROTOCOL ENGINE BLOCK DIAGRAM

Acceptance Filter

RXF2

Identifier

Data Field Data Field

Identifier

Acceptance Mask

RXM1

Acceptance Filter

RXF3

Acceptance Filter

RXF4

Acceptance Filter

RXF5

Acceptance Filter

RXF0

Acceptance Filter

RXF1

TXREQ

TXB2

ABTF

MLOA

TXERR

MESSAGE

Message

Queue

Control Transmit Byte Sequencer

TXREQ

TXB0

ABTF

MLOA

TXERR

MESSAGE

CRC<14:0>

Comparator

Receive<7:0>Transmit<7:0>

Receive

Error

Transmit

Error

Protocol

REC

TEC

ErrPas

BusOff

Finite

State

Machine

Counter

Shift<14:0>

{Transmit<5:0>, Receive<8:0>}

Transmit

Logic

Bit

Timing

Logic

TX RX Configuration

Registers

Clock

Generator

PROTOCOL

ENGINE

BUFFERS

TXREQ

TXB1

ABTF

MLOA

TXERR

MESSAGE

Acceptance Mask

RXM0

SOF

MCP2515

1.5 CAN Protocol Engine

The CAN protocol engin e combines several functiona l

blocks, shown in Figure 1-4 and described be low.

1.5.1 PROTOCOL FINITE STATE

MACHINE

The heart of the engine is the Finite State Machine

(FSM). The FSM is a sequencer that controls the

sequential data stream between the TX/RX shift

also controls the Error Management Logic (EML) and

the parallel data stream between the TX/RX shift

registers and the buffers. The FSM ensures that the

processes of reception, arbitration, transmission and

error-signaling are performed according to the CAN

protocol. The automatic retransmission of messages

on the bus line is also handled by the FSM.

1.5.2 CYCLIC REDUNDANCY CHECK

The Cyclic R edundancy Check register generates the

Cyclic Redundancy Check (CRC) code, which is

transmitte d af ter either the Cont rol Fiel d (for messa ges

with 0 data bytes) or the Data Field and is used to

check the CRC field of incoming messa ges.

1.5.3 ERROR MANAGEMENT LOGIC

The Error Management Logic (EML) is respon sible for

the fault confinement of the CAN device. Its two

counters, the Receive Error Counter (REC) and the

Transmit Error Counter (TEC), are incremented and

decremented by commands from the bit stream

processor. Based on the values of the error counters,

the CAN controller is set into the states error-active,

error-passiv e or bus-off.

1.5.4 BIT TIMING LOGIC

The Bit Timing Logic (BTL) monitors the bus line input

and handles the bus-related bit timing according to the

CAN protocol. The BTL synchronizes on a recessive-

to-dominant bus transition at S t art-of-Frame (hard syn-

chronization) and on any further recessive-to-dominant

bus line transition if the CAN controller itself does not

transmit a dominant bit (resynchronization). The BTL

also provides programmable time segments to

compensate for the propagation delay time, phase

shifts and to define the position of the sample point

within the bit time. The programming of the BTL

depends on the ba ud rate and external physical de lay

times.

FIGURE 1-4: CAN PROTOCOL ENGINE BLOCK DIAGRAM

Bit Timing Logic

CRC<14:0>

Comparator

Receive<7:0> Transmit<7:0>

Sample<2:0>

Majority

Decision

StuffReg<5:0>

Comparator

Transmit Logic

Receive

Error Counter

Transmit

Error Counter

Protocol

FSM

SAM

BusMon

Rec/Trm Addr.

RecData<7:0> TrmData<7:0>

Shift<14:0>

(Transmit<5:0>, Receive<7:0>)

REC

TEC

ErrPas

BusOff

Interface to Standard Buffer

SOF

MCP2515

2.0 CAN MESSAGE FRAMES

The MCP2515 supports standard data frames,

extended data frames and remote frames (standard

and extended), as defined in the CAN 2.0B

specification.

2.1 Standard Data Frame

The CAN standard data frame is shown in Figure 2-1.

As with all other frames, the frame begins with a Start-

Of-Frame (SOF) bit, which is of the dominant state and

allows hard synchronization of all nodes.

The SOF is followed b y the arbitra tion field, consistin g

of 12 bits: the 11-bit identifier and the Remote

Transmission Request (RTR) bit. The RTR bit is used

to distinguish a data frame (RTR bit dominant) from a

remote frame (RTR bit recessive).

Following the arbitration field is the control field,

consisting of six bits. The first bit of this field is the

Identifier Extension (IDE) bit, which must be dominant

to specify a standard frame. The following bit, Reserved

Bit Zero (RB0), is reserved and is defined as a dominant

bit by the CAN pro tocol. The remaining fo ur bits of the

control field are the Data Length Code (DLC), which

specifies the number of bytes of data (0 – 8 bytes)

cont ai ne d i n the message.

After the control field is the data field, which contains

any data bytes that are being sent, and is of the length

defined by the DLC (0 – 8 bytes).

The Cyclic Redundancy Che ck (CRC) field follows the

data field and is used to detect transmission errors. The

CRC field consists of a 15-bit CRC sequence, followed

by the recessive CRC Delimiter bit.

The final field is the two-bit Acknowledge (ACK) field.

During the ACK Slot bit, the transmitting node sends

out a recessive bit. Any node that has received an

error-free frame acknowledges the correct reception of

the frame by sending b ack a dominant b it (regardless

of whether the node is configured to accept that

specific message or not). The recessive acknowledge

delimiter completes the acknowledge field and may not

be overwritten by a dominant bit.

2.2 Extended Data Frame

In the extended CAN data frame, shown in Figure 2-2,

the SOF bit is followed by the arbitration field, which

consists of 32 bits. The first 11 bits are the Most

Significant bits (MSb) (Base-lD) of the 29-bit i dentifier.

These 11 bits are followed by the Substitute Remote

Request (SRR) bit, which is defined to be recessive.

The SRR bit is followed by the lDE bit, which is

recessive to denote an extended CAN frame.

It should be noted that if arbitration remains unresolved

after transmission of the first 1 1 bits of the identifier, and

one of the nodes involved in the arbitration is sendin g

a standard CAN frame (11-bit identifier), the standard

CAN frame will win arbitration due to the assertion of a

dominant lDE bit. Also, the SRR bit in an extended

CAN frame must be recessive to allow the assertion of

a dominant RTR bit by a node that is sending a

standard CAN remote frame.

The SRR and lDE bits are followed by the remaining

18 bits of the identifier (Extended lD) and the remote

transmission request bit.

To enable standard and extended frames to be sent

across a shared network, the 29-bit extended message

identifier is split into 11-bit (most significant) and 18-bit

(least significant) sections. This split ensures that the

lDE bit can remain at the same bit position in both the

standard and extended frames.

Following the arbitra tion fiel d is the six-bit control fi eld.

The first two bits of this field are reserved and must be

dominant. The remaining four bits of the control field

are the DLC, which specifies the number o f d ata bytes

contained in the message.

The remaining portion of the frame (data field, CRC

field, acknowledge field, end-of-frame and intermis-

sion) is constructed in the same way as a standard data

frame (see Section 2.1 “Standard Data Frame”).

2.3 Remote Frame

Normally, data transmission is performed on an

autonomous basis by the data source node (e.g., a

sensor sending out a data frame). It is possible,

however, for a destination node to request data from

the source. To accomplish this, the destination node

sends a remote frame with an identifier that matches

the identifier of the required data frame. The

appropriate data source node will then send a data

frame in response to the remote frame request.

There are two differences between a remote frame

(shown in Figure 2-3) and a data frame. First, the RTR

bit is at the recessive state and, second, there is no

data field. In the event of a data frame and a remote

frame with the same identifier being transmi tted at the

same time, the data frame wins arbitration due to the

dominant RTR bit following the identifier. In this way,

the node that transmitted the remote frame receives

the desired data immediately.

2.4 Error Frame

An error frame is generated by any node that detects a

bus error . An error frame, shown in Figure 2-4, consist s

of two fields: an error flag field followed by an error

delimiter field. There are two types of error flag fields.

The type of error flag field sent depends upon the error

status of the node that detects and generates the error

flag field.

MCP2515

2.4.1 ACTIVE ERRORS

If an error-active node detects a bus error, the node

interrupts transmission of the current message by

generating an active erro r flag. The active error flag is

composed of six consecutive dominant bits. This bit

sequence actively violates the bit-stuffing rule. All other

stations recognize the resulting bit-stuffing error and, in

turn, generate error frames themselves, called error

echo flags.

The error flag field, therefore, consists of between six

and twelve consecutive dominant bits (generated by

one or more nodes). The error delimiter field (eight

recessive bits) completes the error frame. Upon

completion of the error frame, bus activity returns to

normal and the interrupted node attempts to resend the

aborted message.

2.4.2 PASSIVE ERRORS

If an error-passive node detects a bus error, the node

transmits an error-passive flag followed by the error

delimiter field. The error-passive flag consists of six

consecutive recessive bits. The error frame for an error-

passive node consists of 14 recessive bits. From this it

follows that, unless the bus error is detected by an error-

active node or the transmitting node, the message will

continue transmission because the error-passive flag

does not interfere with the bus.

If the transmitting node generates an error-p assive flag,

it will cause other nodes to ge nerate error frame s due

to the resulting bit-stuffing violation. After transmission

of an error frame, an error-passive node must wait for

six consecutive recessive bits on the bus before

attempting to rejoin bus communications.

The error delimiter consists of eight recessive bits and

allows the bus nodes to restart bus communications

cleanly after an error has occurred.

2.5 Overload Frame

An overload f r ame, shown in Figure 2-5, has the same

format as an active error frame. An overload frame,

however, can only be generated during an interframe

space. In this way, an overload frame can be differenti-

ated from an error frame (an error frame i s sent during

the transmission of a message). The overload frame

consists of two fields: an overload flag followed by an

overload delimiter. The overload flag consists of six

dominant bits followed by overlo ad flags genera ted by

other nodes (and, as for an active error flag, giving a

maximum of twelve dominant bits). The overload

delimiter consists of eight recessive bits. An overload

frame can be generated by a node as a result of two

conditions:

1. The node detects a dominant bit during the

interframe space, an illegal condition.

Exception: The dominant bit is detected during

the third bit of IFS. In this case, the receivers will

interpret this as a SOF.

2. Due to internal conditions, the node is not yet

able to begin reception of the next messa ge. A

node may generate a maximum of two

sequential overload frames to delay the start of

the next message.

2.6 Interframe Space

The interframe space separates a preceding frame (of

any type) from a subsequent data or remote frame.

The interframe space is composed of at least three

recessive bits called the Intermission. This allows

nodes time for internal processing before the start of

the next message frame. After the intermission, the

bus line remains in the recessive state (bus idle) until

the next transmission starts.

Note: Error echo flags typically occur when a

localized disturban ce ca uses on e or more

(but not all) nodes to send an error flag.

The remaining nodes generate error fla gs

in response (echo) to the original error

flag.

Note: Case 2 should never occur with the

MCP2515 due to very short internal

delays.

MCP2515

FIGURE 2-1: STANDARD DATA FRAME

0 0 0011111111

Start-of-Frame

Data Frame (number of bits = 44 + 8N)

Arbitration Field

ID 10

ID3

ID0

Identifier

Message

Filtering

Stored in Buffers

RTR

IDE

RB0

DLC3

DLC0

Control

Field

Data

Length

Code

Reserved Bit

8N (0≤N≤8)

Data Field

Stored in Transmit/Receive Buffers

Bit-stuffing

CRC Field

CRC

End-of-

Frame

CRC Del

Ack Slot Bit

ACK Del

IFS

1 1 1

MCP2515

FIGURE 2-2: EXTENDED DAT A FRAME

0 1 1 0 0 0 1

Start-Of-Frame

Arbitration Field

ID10

ID3

ID0

IDE

Identifier

Message

Filtering Stored in Buffers

SRR

EID17

EID0

RTR

RB1

RB0

DLC3

DLC0

Control

Field4

Reserved bits

Data

Length

Code

Stored in Transmit/Receive Buffers

8 8

Data Frame (number of bits = 64 + 8N)

8N (0 ≤ N ≤ 8)

Data Field

1 1 1 1 1 1 1 1

CRC Field

CRC

CRC Del

Ack Slot Bit

ACK Del

End-of-

Frame

Bit-stuffing

IFS

Extended Identifier

111

MCP2515

FIGURE 2-3: REMOTE FRAME

0 1 1 1 0 0

Start-Of-Frame

Arbitration Field

ID10

ID3

ID0

IDE

Identifier

Message

Filtering

SRR

EID17

EID0

RTR

RB1

RB0

DLC3

DLC0

Control

Field4

Reserved bits

Data

Length

Code

Extended Identifier

1 1 1 1 1 1 1 1 1

CRC Field

CRC

CRC Del

Ack Slot Bit

ACK Del

End-of-

Frame

Remote Frame with Extended Identifier

1 1 1

IFS

No data field

MCP2515

FIGURE 2-4: ACTIVE ERROR FRAME

0 0 00

Start-Of-Frame

Interrupted Data Frame

Arbitration Field

ID 10

ID3

ID0

Identifier

Message

Filtering

RTR

IDE

RB0

DLC3

DLC0

Control

Field

Data

Length

Code

Reserved Bit

8N (0≤N≤8)

Data Field

Bit-stuffing

0000000 00111111110

Data Frame or

Remote Frame

Error Frame

Error

Flag

£ 6

Echo

Error

Flag

Error

Delimiter

Inter-Frame Space or

Overload Frame

MCP2515

FIGURE 2-5: OVERLOAD FRAME

0 1 00111111111

Start-Of-Frame

Remote Frame (number of bits = 44)

Arbitration Field

ID 10

ID0

RTR

IDE

RB0

DLC3

DLC0

Control

Field

CRC Field

CRC

End-of-

Frame

CRC Del

Ack Slot Bit

ACK Del

000000011111111

Overload Frame

End-of-Frame or

Error Delimiter or

Overload Delimiter 6

Overload

Flag Overload

Delimiter

8Inter-Frame Space or

Error Frame

MCP2515

NOTES:

MCP2515

3.0 MESSAGE TRANSMISSION

3.1 Transmit Buffers

The MCP2515 implements three transmit buffers. Each

of these buffers occupies 14 bytes of SRAM and are

mapped into the device memory map.

The first byte, TXBnCTRL, is a control register

associated with the message buffer. The information in

this register determines the conditions under which the

message will be transmitted and indicates the status of

the message transmission (see Register 3-2).

Five bytes are used to hold the standard and extended

identifiers, as well as other message arbitration

information (see Register 3-4 through Register 3-7).

The last eight bytes are for the eight possible data

bytes of the message to be transmitted (see

At a minimum, the TXBnSIDH, TXBnSIDL and

TXBnDLC registers must be loaded. If data bytes are

present in the message, the TXBnDm registers must

also be loaded. If the message is to use extended

identifiers, the TXBnEIDm registers must also be

loaded and the TXBnSIDL.EXIDE bit set.

Prior to sending the message , the MCU must initialize

the CANINTE.TXInE bit to enable or disable the

generation of an interru pt when the message is sent.

3.2 Transmit Priority

T ransmit priority is a prioritization within the MCP2515

of the pending transmittable messages. This is

independent from, and not necessarily related to, any

prioritization implicit in the message arbitration scheme

built into the CAN protocol.

Prior to sending the SOF, the priority of all buffers that

are queued for transmission is compared. The transmit

buffer with the highest priority will be sent first. For

example, if transmit buffer 0 has a higher priority setting

than transmit buffer 1, buffer 0 will be sent first.

If two buffers have the same priority settin g, the buffer

with the highest buffer number will be sent first. For

example, if transmit buffer 1 has the same priority

setting as transmit buffer 0, buffer 1 will be sent first.

There are four levels of transmit priority. If

TXBnCTRL.TXP<1:0> for a particular message buffer

is set to 11, that buffer has the highest possible priority .

If TXBnCTRL.TXP<1:0> for a particular message

buffer is 00, that buffer has the lowest possible priority.

3.3 Initiating Transmission

In order to initiate message transmission, the

TXBnCTRL.TXREQ bit must be set for each buffer to

be transmitted. This can be ac complished by:

• Writing to the register via the SPI write command

• Sending the SPI RTS command

• Setting the TXnRTS pi n low for the particular

transmit buffer(s) that are to be transmitted

If transmission is initiated via the SPI interface, the

TXREQ bit can be set at the same time as the TXP

priority bits.

When TXBnCTRL.TXREQ is set, the TXBn CTRL.ABTF,

TXBnCTRL.MLOA and TXBnCTRL.TXERR bits will be

cleared automati ca lly.

Once the transmission has completed successfully, the

TXBnCTRL.TXREQ bit will be cleared, the

CANINTF.TXnIF bit will be set and an interrupt will be

generated if the CANINTE.TXnIE bit is set.

If the message transmission fails, the

TXBnCTRL.TXREQ will remain set. This indicates that

the message is still pending for transmission and one

of the following condition flags will be set:

• If the message started to transmit but encoun-

tered an error condition, the TXBnCTRL.TXERR

and the CANINTF.MERRF bits will be set and an

interrupt will be generated on the INT pin if the

CANINTE.MERRE bit is set

• If the message is lost, arbitration at the

TXBnCTRL.MLOA bit will be set

3.4 One-Shot Mode

One-shot mode ensures that a message will only

attempt to transmit one time. Normally, if a CAN

message loses arbitration, or is destroyed by an error

frame, the message is retransmitted. With One-shot

mode enabled, a message will only attempt to transmit

one time, regardless of arbitration loss or error frame.

One-shot mode is required to maintain time slots in

deterministic systems, such as TTCAN.

Note: The TXBnCTRL.TXREQ bit must be clear

(indicating the transmit buffer is not

pending transmission) before writing to

the transmit buffer.

Note: Setting the TXBnCTRL.TXREQ bit does

not initiate a message transmission. It

merely flags a message buffer as being

ready for transmission. Transmission will

start when the device detects that the bus

is available.

Note: If One-shot mode is enabled

(CANCTRL.OSM), the above conditions

will still exist. However , the TXREQ bit will

be cleared and the message will not

attempt transmission a second time.

MCP2515

3.5 TXnRTS PINS

The TXnRTS pins are input pins that can be configured

as:

• Request-to-send inputs, which provides an

alternative means of initiating the transmission of

a message from any of the transmit buffers

• Standard digital inputs

Configuration and control of these pins is accomplished

using the TXRTSCTRL register (see Register 3-3). The

TXRTSCTRL register can only be modified when the

MCP2515 is in Configuration mode (see Section 10.0

“Modes of Operation” ). If configured to operate as a

request-to-send pin, the pin is mapped into the

respective TXBnCTRL.TXREQ bit for the transmit

buffer. The TXREQ bit is latched by the falling edge of

the TXnRTS pin. The TXnRTS pins are designed to

allow them to be tied directly to the RXnBF pins to

automatically initiate a message transmission when the

RXnBF pin goes low.

The TXnRTS pins have internal pull-up resistors of

100 kΩ (nominal).

3.6 Aborting Transmission

The MCU can request to abort a message in a specific

message buffer by clearing the associated

TXBnCTRL.TXREQ bit.

In addition, all pending messag es can be requ ested to

be aborted by setting the CANCTRL.ABAT bit. This bit

MUST be reset (typically after the TXREQ bits have

been verified to be cleared) to continue transmitting

messages. The CANCTRL.ABTF flag will only be set if

the abort was requested via the CANCTRL.ABAT bit.

Aborting a message by resetting the TXREQ bit does

NOT cause the ABTF bit to be set.

Note: Messages that were transmitting when the

abort was requested will continue to

transmit. If the message does not

successfully complete transmission (i.e.,

lost arbitration or was interrupted by an

error frame), it will then be aborted.

MCP2515

FIGURE 3-1: TRANSMIT MESSAGE FLOWCHART

Start

CAN bus available

to start transmission?

Examine TXBnCTRL.TXP <1:0> to

Are any

TXBnCTRL.TXREQ

bits = 1

The message transmission

sequence begins when the

device determines that the

TXBnCTRL.TXREQ for any of

the transmit registers has been

set.

Clear:

TXBnCTRL.ABTF

TXBnCTRL.MLOA

TXBnCTRL.TXERR

Yes

TXBnCTRL.TXREQ=0

or CANCTRL.ABAT=1

Clearing the TxBnCTRL.TXREQ bi t

while it is set, or setting the CAN-

CTRL.ABA T bit befor e the message

has started transmission, will abort

the message.

Transmit Message

Was

Message Transmitted

Successfully?

Yes

Clear TxBnCTRL.TXREQ

CANINTE.TXnIE=1?

Generate

Interrupt

Yes

Message

Yes

Set

TxBnCTRL.TXERR

Lost

Determine Highest Priority Message

Set

TxBNCTRL.MLOA

The CANINTE.TXnIE bit

determines if an interrupt

should be generated when

a message is successfully

transmitted.

GOTO START

CANTINF.TXnIF

Yes

Message error

Lost arbitration

Arbitration

Error

CANINTE.MEERE?

No Generate

Interrupt

Yes

Set

CANTINF.MERRF

MCP2515

(ADDRESS: 30h, 40h, 50h)

U-0 R-0 R-0 R-0 R/W-0 U-0 R/W-0 R/W-0

— ABTF MLOA TXERR TXREQ — TXP1 TXP0

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 Unimplemented: Read as ‘0’

bit 6 ABTF: Message Aborted Flag bit

1 = Message was aborted

0 = Message completed transmission successfully

bit 5 MLOA: Message Lost Arbitration bit

1 = Message lost arbitration while being sent

0 = Message did not lose arbitra tion while being sent

bit 4 TXERR: Transmission Error Detected bit

1 = A bus error occurred while the message was being transmitted

0 = No bus error occurr ed whi le th e me ssa ge wa s bein g tran smi tted

bit 3 TXREQ: Message Transmit Request bi t

1 = Buffer is currently pending transmission

(MCU sets this bit to request message be transmitted - bit is automatically cleared when

the message is sent)

0 = Buffer is not currently pending transmission

(MCU can clear this bit to request a message abort)

bit 2 Unimplemented: Read as ‘0’

bit 1-0 TXP: Transmit Buffer Priority <1:0> bits

11 = Highest Message Priority

10 = High Intermediate Message Priority

01 = Low Intermediate Message Priority

00 = Lowest Message Priority

MCP2515

(ADDRESS: 0Dh)

U-0 U-0 R-x R-x R-x R/W-0 R/W-0 R/W-0

—— B2RTS B1RTS B0RTS B2RTSM B1RTSM B0RTSM

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 Unimplemented: Read as ‘0’

bit 6 Unimplemented: Read as ‘0’

bit 5 B2RTS: TX2RTS Pin State bit

- Reads state of TX2RTS pin when in Digital Input mode

- Reads as ‘0’ when pin is in ‘Request-to-Send’ mode

bit 4 B1RTS: TX1RTX Pin State bit

- Reads state of TX1RTS pin when in Digital Input mode

- Reads as ‘0’ when pin is in ‘Request-to-Send’ mode

bit 3 B0RTS: TX0RTS Pin State bit

- Reads state of TX0RTS pin when in Digital Input mode

- Reads as ‘0’ when pin is in ‘Request-to-Send’ mode

bit 2 B2RTSM: TX2RTS Pin mode bit

1 = Pin is used to request message transmissi on of TXB2 buffer (on falling edge)

0 = Digital input

bit 1 B1RTSM: TX1RTS Pin mode bit

1 = Pin is used to request message transmissi on of TXB1 buffer (on falling edge)

0 = Digital input

bit 0 B0RTSM: TX0RTS Pin mode bit

1 = Pin is used to request message transmissi on of TXB0 buffer (on falling edge)

0 = Digital input

(ADDRESS: 31h, 41h, 51h)

R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x

SID10 SID9 SID8 SID7 SID6 SID5 SID4 SID3

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-0 SID: Standard Identifier bits <10:3>

MCP2515

(ADDRESS: 32h, 42h, 52h)

R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x

SID2 SID1 SID0 —EXIDE —EID17EID16

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-5 SID: Standard Identifier bits <2:0>

bit 4 Unimplemented: Reads as ‘0’

bit 3 EXIDE: Extended Identifier Enable bit

1 = Message will transmit extended identifier

0 = Message wil l transmit standard identifier

bit 2 Unimplemented: Reads as ‘0’

bit 1-0 EID: Extended Identifier bits <17:16>

(ADDRESS: 33h, 43h, 53h)

R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x

EID15 EID14 EID13 EID12 EID11 EID10 EID9 EID8

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-0 EID: Extended Identifier bits <15:8>

(ADDRESS: 34h, 44h, 54h)

R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x

EID7 EID6 EID5 EID4 EID3 EID2 EID1 EID0

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-0 EID: Extended Identifier bits <7:0>

MCP2515

(ADDRESS: 35h, 45h, 55h)

R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x

—RTR—— DLC3 DLC2 DLC1 DLC0

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 Unimplemented: Reads as ‘0’

bit 6 RTR: Remote Transmission Request bit

1 = Transmitted Message will be a Remote Transmit Request

0 = Transmitted Messag e will be a Data Frame

bit 5-4 Unimplemented: Reads as ‘0’

bit 3-0 DLC: Data Length Code <3:0> bits

Sets the nu mber of data bytes to be transmitted (0 to 8 bytes)

Note: It is possible to set the DLC to a value greater than 8, however only 8 bytes are transmitted

(ADDRESS: 36h - 3Dh, 46h - 4Dh, 56h - 5Dh)

R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x

TXBnDm7 TXBnDm6 TXBnDm5 TXBnDm4 TXBnDm3 TXBnDm2 TXBnDm1 TXBnDm0

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-0 TXBnDM7:TXBnDM0: Transmit Buffer n Data Field Bytes m

MCP2515

NOTES:

MCP2515

4.0 MESSAGE RECEPTION

4.1 Receive Message Buffering

The MCP2515 includes two full receive buffers with

multiple acceptance filters for each. There is also a

separate Message Assembly Buffer (MAB) that acts as

a third receive buffer (see Figure 4-2).

4.1.1 MESSAGE ASSEMBLY BUFFER

Of the three receive buffers, the MAB is always

committed to receiving the next message from the bus.

The MAB assembles all messages received. These

messages will be transferred to the RXBn buffers (See

filter criteria is met.

4.1.2 RXB0 AND RXB1

The remaining two receive buffers, called RXB0 and

RXB1, can receive a complete message from the

protocol engine via the MAB. The MCU can access one

buffer, while the other buffer is available for message

reception, or for holding a previously received

message.

4.1.3 RECEIVE FLAGS/INTERRUPTS

When a message is moved into either of the receive

buffers, the appropriate CANINTF.RXnIF bit is set. This

bit must be cleared by the MCU in order to allow a new

message to be received into the buffer. This bit

provides a positive lockout to ensure that the MCU has

finished with the message before the MCP2515

attempts to load a new message into the receive buffer .

If the CANINTE.RXnIE bit is set, an interrupt will be

generated on the INT pin to indicate that a valid

message has been received. In addition, the

associated RXnBF pin will drive low if configured as a

receive buffer full pin. See Section 4.4 “RX0BF and

RX1BF Pins” for details.

4.2 Receive Priority

RXB0, the higher priority buffer, has one mask and two

message acceptance filters associated with it. The

received message is applied to the mask and filters for

RXB0 first.

RXB1 is the lower priority buffer, with one mask and

four acceptance filters associated with it.

In addition to the message being applied to the RB0

mask and filters first, the lower number of acceptance

filters makes the match on RXB0 more restrictive and

implies a higher priority for that buffer.

When a message is received, bits <3:0> of the

RXBnCTRL register will indicate the acceptance filter

number that enabled reception and whether the

received message is a remote transfer request.

4.2.1 ROLLOVER

Additionally , the RXB0CTRL register can be configured

such that, if RXB0 contains a valid message and

another valid message is received, an overflow error

will not occur and the new message will be moved into

RXB1, regardless of the acceptance criteria of RXB1.

4.2.2 RXM BITS

The RXBnCTRL.RXM bits set special receive modes.

Normally, these bits are cleared to 00 to enable

reception of all valid messages as determined by the

appropriate acceptance filters. In this case, the

determination of whether or not to receive standard or

extended messages is determined by the

RFXnSIDL.EXIDE bit in the acceptance filter register.

If the RXBnCTRL.RXM bits are set to 01 or 10, the

receiver will only accept messages with standard or

extended identifiers, respectively. If an acceptance

filter has the RFXnSIDL.EXIDE bit set such that it does

not correspond with the RXBnCTRL.RXM mode, that

acceptance filter is rendered useless. These two

modes of RXBnCTRL.RXM bits can be used in

systems where it is known that only standard or

extended messages will be on the bus.

If the RXBnCTRL.RXM bits are set to 11, the buffer will

receive all messages, regardless of the values of the

acceptance filters. Also, if a message has an error

before the EOF, that portion of the message assembled

in the MAB before the error frame will be loaded into the

buffer. This mode has some value in debugging a CAN

system and would not be used in an actual system

environment.

Note: The entire contents of the MAB is moved

into the receive buffer once a message is

accepted. This means that, regardless of

the type of identifier (standard or

extended) and the number of data bytes

received, the entire receive buffer is

overwritten with the MAB contents.

Therefore, the contents of all registers in

the buffer must be assumed to have been

modified when any message is received.

MCP2515

4.3 Start-of-Frame Signal

If enabled, the Start-Of-Frame signal is generated on

the SOF pin at the beginning of each CAN message

detected on the RXCAN pin.

The RXCAN pin monitors an idle bus for a recessive-

to-dominant edge. If the dominant condition remains

until the sample point, the DSTEMP interprets this as a

SOF and a SOF pulse is generated. If the dominant

condition does not remain until the sample point, the

DSTEMP interprets this as a glitch on the bus and no

SOF signal is generated. Figure 4-1 illustrates SOF

signalling and glitch-filtering .

As with One-shot mode, one use for SOF signaling is

for TTCAN-type systems. In addition, by monitoring

both the RXCAN pin and the SOF pin, a MCU can

detect early physical bus problems by detecting small

glitches before they affect the CAN communications.

4.4 RX0BF and RX1BF Pins

In addition to the INT pin, which provides an interrupt

signal to the MCU for many different conditions, the

receive buffer full pins (RX0BF and RX1BF) can be

used to indicate that a valid message has been loaded

into RXB0 or RXB1, respectively. T he pins have three

different configurations (Register 4-1):

1. Disabled.

2. Buffer Full Interrupt.

3. Digital Output.

4.4.1 DISABLED

The RXBnBF pins can be disabled to the high-

impedance state by clearing BFPCTRL.BnBFE.

4.4.2 CONFIGURED AS BUFFER FULL

The RXBnBF pins can be configured to act as either

buffer full interrupt pins or as standard digital outputs.

Configuration and status of these pins is available via

the BFPCTRL register (Register 4-3). When set to

operate in Interrupt mode (by setting BFPCTRL.BxBFE

and BFPCTRL.BxBFM bits), these pins are active-low

and are mapped to the CANINTF.RXnIF bit for each

receive buffer. When this bit goes high for one of the

receive buffers (indicating that a valid message has

been loaded into the buffer), the corresponding

RXBnBF pin will go low. When the CANINTF.RXnIF bit

is cleared by the MCU, the correspond ing interrupt pin

will go to the logic-high state until the next messa ge is

loaded into the receive buffer.

FIGURE 4-1: START-OF-FRAME SIGNALING

START-OF-FRAME BIT

Sample

Point

ID BIT

RXCAN

SOF

EXPECTED START-OF-FRAME BIT

Sample

Point BUS IDLE

RXCAN

SOF

Expected

Normal SOF Signaling

Glitch-Filtering

MCP2515

4.4.3 CONFIGURED AS DIGITAL OUTPUT

When used as digital outputs, the BFPCTRL.BxBFM bit

must be cleared and BFPCTRL.BnBFE must be set for

the associated buffer. In this mode, the state of the pin

is controlled by the BFPCTRL.BnBFS bits. Writing a ‘1’

to the BnBFS bit will cause a high level to be driven on

the associated buffer full pin, wh ile a ‘0’ wil l cause the

pin to drive low. When using the pins in this mode, the

state of the pin should be modified only by using the Bit

Modify SPI command to prevent glitches from

occurring on either of the buffer full pins.

TABLE 4-1: CONFIGURING RXNBF PINS

FIGURE 4-2: RECEIVE BUFFER BLOCK DIAGRAM

BnBFE BnBFM BnBFS Pin Status

0XXDisabled, high-impedance

11XReceive buffer interrupt

100Digital output = 0

101Digital output = 1

Acceptance Mask

RXM1

Acceptance Filter

RXF2

Acceptance Filter

RXF3

Acceptance Filter

RXF4

Acceptance Filter

RXF5

Acceptance Mask

RXM0

Acceptance Filter

RXF0

Acceptance Filter

RXF1

Identifier

Data Field Data Field

Identifier

Note: Messages received in the MAB are intially

applied to the mask and filters of RXB0. In

addition, only one filter match occurs (e.g.,

if the message matches both RXF0 and

RXF2, the match will be for RXF0 and the

message will be moved into RXB0).

MCP2515

FIGURE 4-3: RECEIVE FLOW FLOWCHART

Set RXBF0

Start

Detect

Start of

Message?

Valid

Message

Received?

Generate

Error

Meets

a filter criteria

CANINTF.RX0IF = 0?

Go to Start

Move message into RXB0

Set RXB0CTRL.FILHIT <2:0>

CANINTF.RX1IF = 0?

Move message into RXB1

Set CANINTF.RX1IF = 1

Yes

Generate

Interrupt on INT

Yes Yes

No No

Yes

Frame

No Yes

Begin Loading Message into

Message Assembly Buffer (MAB)

according to which filter criteria

was met

Set RXB0CTRL.FILHIT <0>

according to which filter criteria

Set CANSTAT <3:0> accord-

ing to which receive buffer

the message was loade d into

RXB0CTRL.BUKT = 1?

Generate Overflow Error:

Set EFLG.RX1OVR

CANINTE.ERRIE = 1?

Go to Start

Yes

Are

BFPCTRL.B0BFM = 1

BF1CTRL.B0BFE = 1?

and Pin = 0

Set RXBF1

Pin = 0

Yes

CANINTE.RX0IE = 1?CANINTE.RX1IE = 1?

RXB1

RXB0

Set EFLG.RX0OVR

Generate Overflow Error:

Set CANINTF.RX0IF = 1

Are

BFPCTRL.B1BFM = 1

BF1CTRL.B1BFE = 1?

and

Meets

a filter criteria

for RXB1?

for RXB0? No Yes

Generate

Interrupt on INT

Determines if the receive

to accept a new message

Determines if RXB0 can roll

over into RXB1, if it is full.

MCP2515

(ADDRESS: 60h)

U-0 R/W-0 R/W-0 U-0 R-0 R/W-0 R-0 R-0

— RXM1 RXM0 — RXRTR BUKT BUKT1 FILHIT0

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 Unimplemented: Read as ‘0’

bit 6-5 RXM: Receive Buffer Operating Mode bits

11 = Turn mask/filters off; receive any message

10 = Receive only valid messages with extend ed identifiers that meet filter criteria

01 = Receive only valid messages with standard identifiers that meet filter criteria

00 = Receive all valid messages using either standard or extended identifiers th at meet fi lter criteria

bit 4 Unimplemented: Read as ‘0’

bit 3 RXRTR: Received Remote Transfer Request bit

1 = Remote Transfer Request Received

0 = No Remote Transfer Request Received

bit 2 BUKT: Rollover Enable bit

1 = RXB0 message will rollover and be written to RXB1 if RXB0 is full

0 = Rollover disabled

bit 1 BUKT1: Read-only Copy of BUKT bit (used internally by the MCP2515)

bit 0 FILHIT: Filter Hit bit - indicates which acceptance filter enabled reception of message

1 = Acceptance Filter 1 (RXF1)

0 = Acceptance Filter 0 (RXF0)

Note: If a rollover from RXB0 to RXB1 occurs, the FILHIT bit will reflect the filter that accepted

the message that rolled over.

MCP2515

(ADDRESS: 70h)

U-0 R/W-0 R/W-0 U-0 R-0 R-0 R-0 R-0

— RXM1 RXM0 — RXRTR FILHIT2 FILHIT1 FILHIT0

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 Unimplemented: Read as ‘0’

bit 6-5 RXM: Receive Buffer Operating Mode bits

11 = Turn mask/filters off; receive any message

10 = Receive only valid messages with extende d identifiers that meet filter criteria

01 = Receive only valid messages with standard identifiers that meet filter criteria

00 = Receive all valid messages using either standard or extended identifiers that meet filter criteria

bit 4 Unimplemented: Read as ‘0’

bit 3 RXRTR: Received Remote Transfer Request bit

1 = Remote Transfer Request Received

0 = No Remote Transfer Request Received

bit 2-0 FILHIT: Filter Hit bits - indicates which acceptance filter enabled reception of message

101 = Acceptance Filter 5 (RXF5)

100 = Acceptance Filter 4 (RXF4)

011 = Acceptance Filter 3 (RXF3)

010 = Acceptance Filter 2 (RXF2)

001 = Acceptance Filter 1 (RXF1) (Only if BUKT bit set in RXB0CTR L)

000 = Acceptance Filter 0 (RXF0) (Only if BUKT bit set in RXB0CTR L)

MCP2515

(ADDRESS: 0Ch)

U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

—— B1BFS B0BFS B1BFE B0BFE B1BFM B0BFM

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 Unimplemented: Read as ‘0’

bit 6 Unimplemented: Read as ‘0’

bit 5 B1BFS: RX1BF Pin State bit (Digital Output mode only)

- Reads as ‘0’ when RX1BF is configured as interrupt pin

bit 4 B0BFS: RX0BF Pin State bit (Digital Output mode only)

- Reads as ‘0’ when RX0BF is configured as interrupt pin

bit 3 B1BFE: RX1BF Pin Function Enable bit

1 = Pin function enabled, operation mode determined by B1BFM bi t

0 = Pin function disabled, pin goes to high-impe dance state

bit 2 B0BFE: RX0BF Pin Function Enable bit

1 = Pin function enabled, operation mode determined by B0BFM bi t

0 = Pin function disabled, pin goes to high-impe dance state

bit 1 B1BFM: RX1BF Pin Operation Mode bit

1 = Pin is used as interrupt when valid message loaded into RXB1

0 = Digital Output mode

bit 0 B0BFM: RX0BF Pin Operation Mode bit

1 = Pin is used as interrupt when valid message loaded into RXB0

0 = Digital Output mode

(ADDRESS: 61h, 71h)

R-x R-x R-x R-x R-x R-x R-x R-x

SID10 SID9 SID8 SID7 SID6 SID5 SID4 SID3

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-0 SID: Standard Identifier bits <10:3>

These bits contain the eight most significant bits of the Standard Identifier for the received message

MCP2515

(ADDRESS: 62h, 72h)

R-x R-x R-x R-x R-x U-0 R-x R-x

SID2 SID1 SID0 SRR IDE —EID17EID16

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-5 SID: Standard Identifier bits <2:0>

These bits contain the three least significant bits of the Standard Identifier for the received message

bit 4 SRR: Standard Frame Remote Transmit Request bit (valid only if IDE bit = ‘0’)

1 = Standard Frame Remote Transmit Request Received

0 = Standard Data Frame Received

bit 3 IDE: Extended Identifier Flag bit

This bit indicates whether the received message was a Standard or an Extended Frame

1 = Received message was an Extended Frame

0 = Received message was a Standard Frame

bit 2 Unimplemented: Reads as ‘0’

bit 1-0 EID: Extended Identifier bits <17:16>

These bits contain the two most significant bits of the Extended Identifier for the received message

(ADDRESS: 63h, 73h)

R-x R-x R-x R-x R-x R-x R-x R-x

EID15 EID14 EID13 EID12 EID11 EID10 EID9 EID8

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-0 EID: Extended Identifier bits <15:8>

These bits hold bits 15 through 8 of the Extended Identifier for the received message

MCP2515

(ADDRESS: 64h, 74h)

R-x R-x R-x R-x R-x R-x R-x R-x

EID7 EID6 EID5 EID4 EID3 EID2 EID1 EID0

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-0 EID: Extended Identifier bits <7:0>

These bits hold the least significant eight bits of the Extended Identifier for the received message

(ADDRESS: 65h, 75h)

R-x R-x R-x R-x R-x R-x R-x R-x

EID7 EID6 EID5 EID4 EID3 EID2 EID1 EID0

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 Unimplemented: Reads as ‘0’

bit 6 RTR: Extended Frame Remote Transmission Request bit

(valid only when RXBnSIDL.IDE = ‘1’)

1 = Extended Frame Remote Transmit Request Received

0 = Extended Data Frame Received

bit 5 RB1: Reserved Bit 1

bit 4 RB0: Reserved Bit 0

bit 3-0 DLC: Data Length Code bits <3:0>

Indicates number of data bytes that were received

(ADDRESS: 66h - 6Dh, 76h - 7Dh)

R-x R-x R-x R-x R-x R-x R-x R-x

RBnDm7 RBnDm6 RBnDm5 RBnDm4 RBnDm3 RBnDm2 RBnDm1 RBnDm0

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-0 RBnDm7:RBnDm0: Receive Buffer n Data Field Bytes m

Eight bytes containing the data bytes for the received message

MCP2515

4.5 Message Acceptance Filters and

Masks

The message acceptance filters and masks are used to

determine if a message in the message assembly

buffer should be loaded into either of the receive

buffers (see Figure 4-5). Once a valid message has

been received into the MAB, the identifie r fields of the

message are compared to the filter values. If there is a

match, that message will be loaded into the appropriate

receive buffer.

4.5.1 DATA BYTE FILTERING

When receiving standard data frames (1 1-bit identifier),

the DSTEMP automatically applies 16 bits of masks

and filters normally associated with extended

identifiers to the first 16 bits of the data field (data bytes

0 and 1). Figure 4-4 illustrates how masks and filters

apply to extended and standard data frames.

Data byte filtering reduces the load on the MCU when

implementing Higher Layer Protocols (HLPs) that filter

on the first data byte (e.g., DeviceNet™).

4.5.2 FILTER MATCHING

The filter masks (see Register 4-14 through

identifier are examined with the filters. A truth table is

shown in Table 4-2 that indicates how each bit in the

identifier is compared to the masks and filters to deter-

mine if the message should be loaded into a receive

buffer. The mask essentially determines which bits to

apply the acceptance filters to. If any mask bit is set to

a zero, that bit will automatically be accepted,

regardless of the filter bit.

TABLE 4-2: FILTER/MASK TRUTH TABLE

As shown in the receive buffers block diagram

(Figure 4-2), acceptance filters RXF0 and RXF1 (and

filter mask RXM0) are associated with RXB0. Filters

RXF2, RXF3, RXF4, RXF5 and mask RXM1 are

associated with RXB1.

FIGURE 4-4: MASKS AND FILTERS APPLY TO CAN FRAMES

Mask Bit

nFilter Bit n Message

Identifier

bit

Accept or

Reject bit

0X X

10 0

10 1

Reject

11 0

Reject

11 1

Note: X = don’t care

Extended Frame

Standard Data Frame

ID10 ID0 EID17 EID0

Masks and Filters apply to the entire 29-bit ID field

ID10 ID0 Data Byte 0 Data Byte 1

11-bit ID Standard frame

16-bit data filtering *

* The two MSb (EID17 and EID16) mask and filter bits are not used.

MCP2515

4.5.3 FILHIT BITS

Filter matches on received messages can be

determined by the FILHIT bits in the associated

RXBnCTRL register. RXB0CTRL.FILHIT0 for buffer 0

and RXB1CTRL.FILHIT<2:0> for buffer 1.

The three FILHIT bits for receive buffer 1 (RXB1) are

coded as follows:

-101 = Acceptance Filter 5 (RXF5)

-100 = Acceptance Filter 4 (RXF4)

-011 = Acceptance Filter 3 (RXF3)

-010 = Acceptance Filter 2 (RXF2)

-001 = Acceptance Filter 1 (RXF1)

-000 = Acceptance Filter 0 (RXF0)

RXB0CTRL contains two copies of the BUKT bit and

the FILHIT<0> bit.

The coding of th e BUKT bit enables these three bits to

be used similarly to the RXB1C TRL.F ILHIT bits and to

distinguish a hit on filter RXF0 and RXF1 in either

RXB0 or after a roll over into RXB1.

-111 = Acceptance Filter 1 (RXB1)

-110 = Acceptance Filter 0 (RXB1)

-001 = Acceptance Filter 1 (RXB0)

-000 = Acceptance Filter 0 (RXB0)

If the BUKT bit is clear, there are six codes

corresponding to the six filters. If the BUKT bit is set,

there are six codes corresponding to the six filters, plus

two additional codes corresponding to RXF0 and RXF1

filters that rol l ov er in to RXB1.

4.5.4 MULTIPLE FILTER MATCHES

If more than one acceptance filter matches, the FILHIT

bits will encode the binary value of the lowest

numbered filter that matched. For example, if filter

RXF2 and filter RXF4 match, FILHIT will be loaded with

the value for RXF2. This essentially prioritizes the

acceptance filters with a lower-numbered filter having

higher priority. Messages are compared to filters in

ascending order of filter number. This also insures that

the message will only be received into one buffer. This

implies that RXB0 has a higher prio rity than RXB1.

4.5.5 CONFIGURING THE MASKS AND

FILTERS

The mask and filter registers can only be modified

when the MCP2515 is in Configuration mode (see

Section 10.0 “Modes of Operatio n” ).

FIGURE 4-5: MESSAGE ACCEPT ANCE MAS K AND FILTER OPERATION

Note: 000 and 001 can only occur if the BUKT bit

in RXB0CTRL is set, allowing RXB0

messages to roll over into RXB1.

Acceptance Filter Register Acceptance Mask Register

RxRqst

Message Assembly Buffer

RXFn0

RXFn1

RXFnn

RXMn0

RXMn1

RXMnn

Identifier

MCP2515

(ADDRESS: 00h, 04h, 08h, 10h, 14h, 18h)

R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x

SID10 SID9 SID8 SID7 SID6 SID5 SID4 SID3

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-0 SID: Standard Identifier Fil ter bits <10:3>

These bits hold the filter bits to be applied to bits <10:3> of the S tandard Identifier portion of a received

message

(ADDRESS: 01h, 05h, 09h, 11h, 15h, 19h)

R/W-x R/W-x R/W-x U-0 R/W-x U-0 R/W-x R/W-x

SID2 SID1 SID0 —EXIDE —EID17EID16

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-5 SID: Standard Identifier Filter bits <2:0>

These bits hold the filter bits to be applied to bits <2:0> of the St andard Identifier portion of a received

message

bit 4 Unimplemented: Reads as ‘0’

bit 3 EXIDE: Extended Identifier Enable bit

1 = Filter is applied only to Extended Frames

0 = Filter is applied only to Standard Frames

bit 2 Unimplemented: Reads as ‘0’

bit 1-0 EID: Extended Identifier Filter bits <17:16>

These bits hold the filter bits to be applied to bits <17:16> of the Extended Identifier portion of a

received message

MCP2515

(ADDRESS: 02h, 06h, 0Ah, 12h, 16h, 1Ah)

R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x

EID15 EID14 EID13 EID12 EID11 EID10 EID9 EID8

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-0 EID: Extended Identifier bits <15:8>

These bits hold the filter bits to be applied to bits <15:8> of the Extended Identifier portion of a received

message

(ADDRESS: 03h, 07h, 0Bh, 13h, 17h, 1Bh)

R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x R/W-x

EID7 EID6 EID5 EID4 EID3 EID2 EID1 EID0

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-0 EID: Extended Identifier bits <7:0>

These bits hold the filter bits to be applied to the bits <7:0> of the Extended Identifier portion of a

received message

(ADDRESS: 20h, 24h)

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

SID10 SID9 SID8 SID7 SID6 SID5 SID4 SID3

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-0 SID: Standard Identifier Mask bits <10:3>

These bits hold the mask bits to be applied to bits <10:3> of the Standard Identifier portion of a received

message

MCP2515

(ADDRESS: 21h, 25h)

R/W-0 R/W-0 R/W-0 U-0 U-0 U-0 R/W-0 R/W-0

SID2 SID1 SID0 — — —EID17EID16

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-5 SID: Standard Identifier Mask bits <2:0>

These bits hold the mask bits to be applied to bits<2:0> of the S tandard Identifier portion of a received

message

bit 4-2 Unimplemented: Reads as ‘0’

bit 1-0 EID: Extended Identifier Mask bits <17:16>

These bits hold the mask bits to be applied to bits <17:16> of the Extended Identifier portion of a

received message

(ADDRESS: 22h, 26h)

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

EID15 EID14 EID13 EID12 EID11 EID10 EID9 EID8

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-0 EID: Extended Identifier bits <15:8>

These bits hold the filter bits to be applied to bits <15:8> of the Extended Identifier portion of a received

message

(ADDRESS: 23h, 27h)

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

EID7 EID6 EID5 EID4 EID3 EID2 EID1 EID0

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-0 EID: Extended Identifier Mask bits <7:0>

These bits hold the mask bits to be applied to the bits <7:0> of the Extended Identifier portion of a

received message

MCP2515

5.0 BIT TIMING

All nodes on a given CAN bus must have the same

nominal bit rate. The CAN protocol uses Non Return to

Zero (NRZ) coding, which does not encode a clock

within the data stream. Therefore, the receive clock

must be recovered by the receiving nodes and

synchronized to the transmitter’s clock.

As oscillators and transmission times may vary from

node to node, the receiver must have some type of

Phase Lock Loop (PLL) synchronized to data

transmission edges to synchronize and maintain the

receiver clock. Since the data is NRZ-coded, it is

necessary to include bit-stuffing to insure that an edge

occurs at least every six bit times to maintain the Digital

Phase Lock Loop (DPLL) synchronization.

The bit timing of the MCP2515 is implemented using a

DPLL that is configured to synchronize to the incoming

data, as well as provide the nominal timing for the

transmitted data. The DPLL breaks each bit time into

multiple segments made up of minimal periods of time,

called the Time Quanta (TQ).

Bus timing functions executed within the bit time frame

(such as synchronization to the local oscillator, network

transmission delay compensation and sample point

positioning) are defined by the programmable bit timing

logic of the DPLL.

5.1 The CAN Bit TIme

All devices on the CAN bus must use the same bit rate.

However , all devices are not required to have the same

master oscillator clock frequency. For the different

clock frequencies of the individual device s, the bit rate

has to be adjusted by appropriately setting the baud

rate prescaler and number of time quanta in each

segment.

The CAN bit time is made up of non-overlapping

segments. Each of these segments are made up of

integer units called Time Quanta (TQ), explained later

in this data sheet. The Nominal Bit Rate (NBR) is

defined in the CAN spe cification as the number of bi ts

per second transmitte d by an ideal transmitter with no

resynchronization. It can be described with the

equation:

EQUATION 5-1:

Nominal Bit Time

The Nominal Bit Time (NBT) (tbit) is made up of non-

overlapping segments (Figure 5-1). Therefore, the

NBT is the summation of the following segments:

Associated with the NBT are the sample point,

Synchronization Jump Width (SJW) and Information

Processing Time (IPT), which are explained later.

SYNCHRONIZATION SEGMENT

The Synchronization Segment (SyncSeg) is the first

segment in the NBT and is used to synchronize the

nodes on the bus. Bit edges are expected to occur

within the SyncSeg. This segment is fixed at 1 TQ.

FIGURE 5-1: CAN BIT TIME SEGMENTS

NBR fbit 1

tbit

-------==

tbit tSyncSeg tPropSeg tPS1 tPS2

+++=

Nominal Bit Time (NBT), tbit

Sample

Point

SyncSeg PropSeg PhaseSeg1 (PS1) PhaseSeg2 (PS2)

MCP2515

PROPAGATION SEGMENT

The Propagation Segment (PropSeg) exists to

compensate for physical delays between nodes. The

propagation delay is defined as twice the sum of the

signal’s propagation time on the bus line, in cl uding th e

delays associated with the b us driver. The Pro pSeg is

programmable from 1 – 8 TQ.

PHASE SEGMENT 1 (PS1) AND PHASE

SEGMENT 2 (PS2)

The two phase segments, PS1 and PS2, are used to

compensate for edge phase errors on the bus. PS1 can

be lengthened (or PS2 shortened) by resyncronization.

PS1 is programmable from 1 – 8 TQ and PS2 is

programmable from 2 – 8 TQ.

SAMPLE POINT

The sample point is the point in the bit time at which the

logic level is read and interp reted. The samp le point is

located at the end of PS1. The exception to this rule is

if the sample mode is configured to sample three times

per bit. In this case, while the bit is still sampled at the

end of PS1, two additional samples are taken at one-

half TQ intervals prior to the end of PS1, with the value

of the bit being determined by a majori ty decision.

INFORMATION PROCESSING TIME

The Information Processing Time (IPT) is the time

required for the logic to determine the bit level of a

sampled bit. The IPT begins at the sample point, is

measured in TQ and is fixed at 2 TQ for the Microchi p

CAN module. Since PS2 also begins at the sample

point and is the last segment in the bit time, it is

required that the PS2 minimum is not less than the IPT.

Therefore:

SYNCHRONIZATION JUMP WIDTH

The Synchronization Jump Width (SJW) adjusts the bit

clock as necessary by 1 – 4 TQ (as configured) to

maintain synchronization with the transmitted

message. Synchronization is covered in more detail

later in this data sheet.

Time Quantum

Each of the segmen ts that make up a bit time are made

up of integer units called Time Quanta (TQ). The length

of each T ime Quantum is based on the oscillator period

(tOSC). The base TQ equals twice the oscillator period.

Figure 5-2 shows how the bit period is derived from

TOSC and TQ. The TQ length equals one TQ clock

period (tBRPCLK), which is programmable using a

programmable prescaler, called the Baud Rate

Prescaler (BRP). This is illustrated in the following

equation:

EQUATION 5-2:

FIGURE 5-2: TQ AND THE BIT PERIOD

PS2min IPT 2TQ==

TQ 2 BRP TOSC

⋅⋅ 2 BRP⋅

FOSC

-------------------==

Where: BRP equals the configuration as shown in

tOSC

TBRPCLK

tBIT Sync

(fixed) PropSeg

(Programmable) PS2

(Programmable)

PS1

(Programmable)

(tTQ)

CAN Bit Time

MCP2515

5.2 Synchronization

To compensate for phase shifts between the oscil lator

frequencies of each of the nodes on the bus, each CAN

controller must be able to synchronize to the relevant

signal edge of the incoming signal. Synchro nization is

the process by which the DPLL function is

implemented.

When an edge in th e transmitted data is detected, the

logic will compare the location of the edge to the

expected time (SyncSeg). The circuit will then adjust

the values of PS1 and PS2 as necessary.

There are two mechanisms used for synchronization:

1. Hard synchronization.

2. Resynchronization.

5.2.1 HARD SYNCHRONIZATION

Hard synchronization is only performed when there is a

recessive-to-dominant edge during a BUS IDLE

condition, indicating the start of a message. After hard

synchronization, the bit time counters are restarted with

SyncSeg.

Hard synchronization forces the edge that has

occurred to lie within the synchronization segment of

the restarted bit time. Due to the rules of

synchronization, if a hard synchronization occurs, there

will not be a resynchronization within that bit time.

5.2.2 RESYNCHRONIZATION

As a result of resynchronization, PS1 may be

lengthened or PS2 may be shortened. The amount of

lengthening or shortening of the phase buffer segments

has an upper-bound, given by the Synchronization

Jump Width (SJW).

The value of the SJW will be added to PS1 or

subtracted from PS2 (see Figure 5-3). The SJW

represents the loop filtering of the DPLL. The SJW is

programmable between 1 TQ and 4 TQ.

5.2.2.1 Phase Errors

The NRZ bit coding method does not encode a clock

into the message. Clocking information will only be

derived from recessive-to-dominant transitions. The

property which states that only a fixed maximum

number of successive bits have the same value (bit-

stuffing) ensures resynchronization to the bit stream

during a frame.

The phase erro r of an edge is given by the position of

the edge relative to SyncSeg, measured in TQ. The

phase error is define d i n ma gni tu de of TQ as follows:

• e = 0 if the edge lies within SYNCSEG.

• e > 0 if the edge lies before the SAMPLE POINT

(TQ is added to PS1).

• e < 0 if the edge lies after the SAMPLE POINT of

the previous bit (TQ is subtracted from PS2).

5.2.2.2 No Phase Error (e = 0)

If the magnitude of the phase error is less than or equal

to the programmed value of the SJW, the effect of a

resynchronization is the same as that of a hard

synchronization.

5.2.2.3 Positive Phase Error (e > 0)

If the magnitude of the phase error is larger than the

SJW and, if the phase error is positive, PS1 is

lengthened by an amount equal to the SJW.

5.2.2.4 Negative Phase Error (e < 0)

If the magnitude of the phase error is larger than the

resynchronization jump width and the phase error is

negative, PS2 is shortened by an amount equal to the

SJW.

5.2.3 SYNCHRONIZATION RULES

1. Only recessive-to-dominant edges will be used

for synchronization.

2. Only one synchronization within one bit time is

allowed.

3. An edge will be used for syn chronization only if

the value detected at th e previ ous samp le p oint

(previously read bus value) differs from the bus

value immediately after the edge.

4. A transmitting node will no t resynchronize on a

positive phase error (e > 0).

5. If the absolute magnitude of the phase error is

greater than the SJW, the appropriate phase

segment will adjust by an amount equal to the

SJW.

MCP2515

FIGURE 5-3: SYNCHRONIZING THE BIT TIME

SyncSeg PropSeg PhaseSeg1 (PS1) PhaseSeg2 (PS2)

Sample

Point

SyncSeg PropSeg PhaseSeg1 (PS1) PhaseSeg2 (PS2)

Sample

Point

SyncSeg PropSeg PhaseSeg1 (PS1) PhaseSeg2 (PS2)

Sample

Point

Nominal Bit Time (NBT)

SJW (PS1)

SJW (PS2)

Nominal Bit T ime (NBT)

SJW (PS1)

SJW (PS2)

Actual Bit T i me

Resynchronization to a Slowe r Transmitter (e > 0)

Input Signal

Input Signal (e < 0)

SJW (PS1)

SJW (PS2)

Nominal Bit Time (NBT)

Actual Bit Time

Resynchronization to a Faster Transmitter (e < 0)

Input Signal (e = 0)

No Resynchronization (e = 0)

(e > 0)

MCP2515

5.3 Programming Time Segments

Some requirements for programming of the time

segments:

• PropSeg + PS1 >= PS2

• PropSeg + PS1 >= TDELAY

• PS2 > SJW

For example, assu ming that a 125 kHz CAN baud rate

with FOSC = 20 MHz is desired:

TOSC = 50 ns, choose BRP<5:0> = 04h, then

TQ= 500 ns. To obtain 125 kHz, the bit time must be 16

TQ.

Typically, the sampling of the bit should take place at

about 60-70% of the bit time, depending on the system

parameters. Also, typically, the TDELAY is 1-2 TQ.

SyncSeg = 1 TQ and PropSeg = 2 TQ. So setting

PS1 = 7 TQ would place the sample at 10 TQ after the

transition. This would leave 6 TQ for PS2.

Since PS2 is 6, according to the rules, SJW could be a

maximum of 4 TQ. However, a large SJW is typically

only necessary when the clock generation of the differ-

ent nodes is inaccurate or unstable, such as using

ceramic resonators. So a SJW of 1 is usually enough.

5.4 Oscillator Tolerance

The bit timing requirements allow ceramic resonators

to be used in applications with transmission rates of up

to 125 kbit/sec as a rule of thumb. For the full bus

speed range of the CAN prot ocol, a quartz oscill ator is

required. A maximum node-to-node oscillator variation

of 1.7% is allowed.

5.5 Bit Timing Configuration

Registers

The configuration registers (CNF1, CNF2, CNF3)

control the bit timing for the CAN bus interface. These

registers can only be modified when the MCP2515 is in

Configuration mode (see Section 10.0 “Modes of

Operation”).

5.5.1 CNF1

The BRP<5:0> bits control the baud rate prescaler.

These bits set the length of TQ relative to the OSC1

input frequency, with the minimum TQ length being

OSC (when BRP<5:0> = ‘b000000’). The

SJW<1:0> bits select the SJW in terms of number of

TQs.

5.5.2 CNF2

The PRSEG<2:0> bits set the length (in TQ’s) of the

propagation segment. The PHSEG1<2:0> bits set the

length (in TQ’s) of PS1.

The SAM bit controls how many times the RXCAN pin

is sampled. Setting this bit to a ‘1’ causes the bus to be

sampled three times: twice at TQ/2 before the sa mple

point and once at the normal sample point (which is at

the end of PS1). The value of the bus is determined to

be the majority sampled. If the SAM bit is set to a ‘0’,

the RXCAN pin is sampled only once at the sample

point.

The BTLMODE bit controls how the length of PS2 is

determined. If this bit is set to a ‘1’, the length of PS2 is

determined by the PHSEG2<2:0> bits of CNF3 (see

Section 5.5.3 “CNF3”). If the BTLMODE bit is set to a

‘0’, the length of PS2 is greater than that of PS1 and the

information processing time (which is fixed at 2 T Q for

the MCP2515).

5.5.3 CNF3

The PHSEG2<2:0> bits set the length (in TQ’s) of PS2,

if the CNF2.BTLMODE bit is set to a ‘1’. If the

BTLMODE bit is set to a ‘0’, the PHSEG2<2:0> bits

have no effect.

MCP2515

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

SJW1 SJW0 BRP5 BRP4 BRP3 BRP2 BRP1 BRP0

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-6 SJW: Synchronization Jump Width Length bits <1:0>

11 = Length = 4 x TQ

10 = Length = 3 x TQ

01 = Length = 2 x TQ

00 = Length = 1 x TQ

bit 5-0 BRP: Baud Rate Prescaler bits <5:0>

TQ = 2 x (BRP + 1)/FOSC

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

BTLMODE SAM PHSEG12 PHSEG11 PHSEG10 PRSEG2 PRSEG1 PRSEG0

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 BTLMODE: PS2 Bit Time Length bit

1 = Length of PS2 determined by PHSEG22:PHSEG20 bits of CNF3

0 = Length of PS2 is the greater of PS1 and IPT (2 TQ)

bit 6 SAM: Sample Point Configuration bit

1 = Bus line is sampled three times at the sample point

0 = Bus line is sampled once at the sample point

bit 5-3 PHSEG1: PS1 Length bits<2:0>

(PHSEG1 + 1) x TQ

bit 2-0 PRSEG: Propagation Segment Length bits <2:0>

(PRSEG + 1) x TQ

MCP2515

R/W-0 R/W-0 U-0 U-0 U-0 R/W-0 R/W-0 R/W-0

SOF WAKFIL — — — PHSEG22 PHSEG21 PHSEG20

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 SOF: Start-of-Frame signal bit

If CANCTRL.CLKEN = 1:

1 = CLKOUT pin enable d for SOF signal

0 = CLKOUT pin enabled for clockout function

If CANCTRL.CLKEN = 0, Bit is don’t care.

bit 6 WAKFIL: Wake-up Filter bit

1 = Wake-up filter enabled

0 = Wake-up filter disabled

bit 5-3 Unimplemented: Reads as ‘0’

bit 2-0 PHSEG2: PS2 Length bits<2:0>

(PHSEG2 + 1) x TQ

Minimum valid setting for PS2 is 2 TQ

MCP2515

NOTES:

MCP2515

6.0 ERROR DETECTION

The CAN protocol provides sophisticated error

detection mechanisms. The following errors can be

detected.

6.1 CRC Error

With the Cyclic Redundancy Check (CRC), the

transmitter calculates special check bits for the bit

sequence from the start of a frame until the end of the

data field. This CRC sequence is transmitted in the

CRC Field. The receiving node also calculates the

CRC sequence using the same formula and performs

a comparison to the received sequence. If a mismatch

is detected, a CRC error has occurred and an error

frame is generated. The me ssage is repeated.

6.2 Acknowledge Error

In the acknowledge fie ld of a message, the tran smitter

checks if the acknowledge slot (which has been sent

out as a recessive bit) contains a dominant bit. If not, no

other node has received the frame correctly. An

acknowledge error has occurred, an error frame is

generated and the message will have to be repeated.

6.3 Form Error

If a node detects a dominant bit in one of the four

segments (including end-of-frame, interframe space,

acknowledge delimi ter or CRC delimiter), a form error

has occurred and an error frame is generated. The

message is repeated.

6.4 Bit Error

A bit error occurs if a transmitter detects the opposite

bit level to what it transmitted (i.e., transmitted a

dominant and detected a recessive, or transmitted a

recessive and detected a dominant).

Exception: In the ca se where the transmitter sends a

recessive bit and a dominan t bit is de tected during th e

arbitration field and the acknowledge slot, no bit error is

generated because normal arbitrati on is occurring.

6.5 Stuff Error

lf, between the start-of-frame and the CRC delimiter,

six consecutive bits with the same polarity are

detected, the bit-stuffing rule has been violated. A stuff

error occurs and an error frame is generated. The

message is repeated.

6.6 Error States

Detected errors are made known to all other nodes via

error frames. The transmission of the erroneous mes-

sage is aborted an d the frame i s repeated as soon as

possible. Furthermore, each CAN node is in one of the

three error states according to the value o f the internal

error counters:

1. Error-active.

2. Error-passive.

3. Bus-off (transmitter only).

The error-active state is the usual state where the node

can transmit messages and active error frames (ma de

of dominant bits) without any restrictions.

In the error-passive st ate, messages and passive error

frames (made of recessive bits) may be transmitted.

The bus-off state makes it temporarily impossible for

the station to participate in the bus communication.

During this state, messages can neither be received or

transmitted. Only transmitters can go bus-off.

6.7 Error Modes and Error Counters

The MCP2515 contains two error counters: the

Receive Error Counter (REC) (see Register 6-2) and

the Transmit Error Counter (TEC) (see Register 6-1).

The values of both counte rs can be read by the MCU.

These counters are incremented/decremented in

accordance with the CAN bus specification.

The MCP2515 is error-active if both error counters are

below the error-passive limit of 128.

It is error-passive if at least one of the error counters

equals or exceeds 128.

It goes to bus-off if the TEC exceeds the bus-off limit of

255. The device remains in this state until the bus-off

recovery sequence is received. The bus-off recovery

sequence consists of 128 occurrences and 11 consec-

utive recessive bits (see Figure 6-1).

The Current Error mode of the MCP2 515 can be read

by the MCU via the EFLG register (see Register 6-3).

Additionally, there is an error state warning flag bit

(EFLG:EW ARN) which is set if at least one of the error

counters equals or exceeds the error warning limit of

96. EW ARN is reset if both error counters are less than

the error warning limit.

Note: The MCP2515, after going bus-off, will

recover back to error-active without any

intervention by the MCU if the bus remains

idle for 128 x 11 bit times. If this is not

desired, the error interrupt service routine

should address this.

MCP2515

FIGURE 6-1: ERROR MODES ST ATE DIAGRAM

Bus-Off

Error-Active

Error-Passive

REC < 127 or

TEC < 127

REC > 127 or

TEC > 127

TEC > 255

RESET

128 occurrences of

11 consecutive

“recessive” bits

(ADDRESS: 1Ch)

R-0 R-0 R-0 R-0 R-0 R-0 R-0 R-0

TEC7 TEC6 TEC5 TEC4 TEC3 TEC2 TEC1 TEC0

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-0 TEC: Transmit Error Count bits <7:0>

(ADDRESS: 1Dh)

R-0 R-0 R-0 R-0 R-0 R-0 R-0 R-0

REC7 REC6 REC5 REC4 REC3 REC2 REC1 REC0

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-0 REC: Receive Error Count bits <7:0>

MCP2515

(ADDRESS: 2Dh)

R/W-0 R/W-0 R-0 R-0 R-0 R-0 R-0 R-0

RX1OVR RX0OVR TXBO TXEP RXEP TXWAR RXWAR EWARN

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 RX1OVR: Receive Buffer 1 Overflow Flag bit

- Set when a valid message is received for RXB1 and CANINTF.RX1IF = 1

- Must be reset by MCU

bit 6 RX0OVR: Receive Buffer 0 Overflow Flag bit

- Set when a valid message is received for RXB0 and CANINTF.RX0IF = 1

- Must be reset by MCU

bit 5 TXBO: Bus-Off Error Flag bit

- Bit set when TEC reaches 255

- Reset after a successful bus recovery sequence

bit 4 TXEP: T ransmit Error-Passive Flag bit

- Set when TEC is equal to or greater than 128

- Reset when TEC is less than 128

bit 3 RXEP: Receive Error-Passive Flag bit

- Set when REC is equal to or greater than 128

- Reset when REC is less than 128

bit 2 TXWAR: T ransmit Error Warning Flag bit

- Set when TEC is equal to or greater than 96

- Reset when TEC is less than 96

bit 1 RXWAR: Rece ive Error Warning Flag bit

- Set when REC is equal to or greater than 96

- Reset when REC is less than 96

bit 0 EWARN: Error Warning Flag bit

- Set when TEC or REC is equal to or greater than 96 (TXWAR or RXWAR = 1)

- Reset when both REC and TEC are less than 96

MCP2515

NOTES:

MCP2515

7.0 INTERRUPTS

The MCP2515 has eight sources of interrupts. The

CANINTE register contains the individual interrupt

enable bits for each interrupt source. The CANINTF

each interrupt source. When an interrupt occurs, the

INT pin is driven lo w by the MCP2515 and will remain

low until the interrupt is cleared by the MCU. An

interrupt can not be cleared if the respective condition

still prevails.

It is recommended that the bit modify command be

used to reset flag bits in the CANINTF register rather

than normal write operations. This is done to prevent

unintentionally changing a flag that changes during the

write command, potentially causing an interrupt to be

missed.

It should be noted that the CANINTF flags are

read/write and an interrupt can be generated by the

MCU setting any of these bits, provided the associated

CANINTE bit is also set.

7.1 Interrupt Code Bits

The source of a pending interrupt is indicated in the

CANSTAT.ICOD (interrupt code) bits, as indicated in

occur, the INT will remain low until all interrupts have

been reset by the MCU. The CANSTAT.ICOD bits will

reflect the code for the highest priority interrupt that is

currently pending. Interrupts are internally prioritized

such that the lower the ICOD value, the higher the

interrupt priority. Once the highest priority interrupt

condition has been cleared, the code for the next

highest priority interrupt that is pending (if any) will b e

reflected by the ICOD bits (see Table 7-1). Only those

interrupt sources that have their associated CANINTE

enable bit set will be reflected in the ICOD bits.

TABLE 7-1: ICOD<2:0> DECODE

7.2 Transmit Interrupt

When the transmit interrupt is enabled

(CANINTE.TXnIE = 1), an interrupt will be generated on

the INT pin once the associated transmit buffer

becomes empty and is ready to be loaded with a new

message. The CANINTF.TXnIF bit will be set t o indicate

the source of the interrupt. The interrupt is cleared by

clearing the TXnIF bi t.

7.3 Receive Interrupt

When the receive interrupt is enabled

(CANINTE.RXnIE = 1), an interrupt will be generated

on the INT pin once a message has been successfu lly

received and loaded into the associated receive buffer.

This interrupt is activated immediately after receiving

the EOF field. The CANINTF.RXnIF bit will be set to

indicate the source of the interrupt. The interrupt is

cleared by clearing the RXnIF bit.

7.4 Message Error Interrupt

When an error occurs during the transmission or

reception of a message, the message error flag

(CANINTF.MERRF) will be set and, if the

CANINTE.MERRE bit is set, an interrupt will be gener-

ated on the INT pin. This is intended to be used to

facilitate baud rate determination when used in

conjunction with Listen-only mode.

7.5 Bus Activity Wakeup Interrupt

When the MCP2515 is in Sleep mode and the bus activ-

ity wakeup interrupt is enabled (CANINTE.WAKIE = 1),

an interrupt will be generated on the INT pin and the

CANINTF.WAKIF bit will be set when activity is det ected

on the CAN bus. This interrupt cause s the MCP2515 to

exit Sleep mode. The interrupt is reset by clearing the

WAKIF bit.

7.6 Error Interrupt

When the error interrupt is enabled

(CANINTE.ERRIE = 1), an interrupt is generated on

the INT pin if an overflow condition occurs or if the error

state of the transmitter or receiver has changed. The

Error Flag (EFLG) register will indicate one of the

following conditions.

7.6.1 RECEIVER OVERFLOW

An overflow condition occurs when the MAB has

assembled a valid receive message (the message

meets the criteria of the acceptance filters) and the

receive buffer associated with the filter is not availab le

for loading of a new message. The associated

EFLG.RXnOVR bit will be set to indicate the overflow

condition. Thi s bi t mu st be cle a red by th e MC U .

ICOD<2:0> Boolean Expression

000 ERR•WAK•TX0•TX1•TX2•RX0•RX1

001 ERR

010 ERR•WAK

011 ERR•WAK•TX0

100 ERR•WAK•TX0•TX1

101 ERR•WAK•TX0•TX1•TX2

110 ERR•WAK•TX0•TX1•TX2•RX0

111 ERR•WAK•TX0•TX1•TX2•RX0•RX1

Note: ERR is associated with CANINTE,ERRIE.

Note: The MCP2515 wakes up into Listen-only

mode.

MCP2515

7.6.2 RECEIVER WARNING

The REC has reached the MCU warning limit of 96.

7.6.3 TRANSMITTER WARNING

The TEC has reached the MCU warning limit of 96.

7.6.4 RECEIVER ERROR-PASSIVE

The REC has exceeded the error-passive limit of 127

and the device has gone to error-passive state.

7.6.5 TRANSMITTER ERROR-PASSIVE

The TEC has exceeded the error- passive limit of 127

and the device has gone to error- passive state.

7.6.6 BUS-OFF

The TEC has exceede d 255 and the device has go ne

to bus-off state.

7.7 Interrupt Acknowledge

Interrupts are directly associated with one or more sta-

tus flags in the CANINTF regi ster. Interrupts are pend-

ing as long as one of the flags is set. Once an interrupt

flag is set by the device, the flag can not be reset by the

MCU until the interrupt condition is removed.

(ADDRESS: 2Bh)

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

MERRE WAKIE ERRIE TX2IE TX1IE TX0IE RX1IE RX0IE

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 MERRE: Message Error Interrupt Enable bit

1 = Interrupt on error during message reception or transmission

0 =Disabled

bit 6 WAKIE: Wakeup Interrupt Enable bit

1 = Interrupt on CAN bus activity

0 =Disabled

bit 5 ERRIE: Error Interrupt Enable bit (multiple sources in EFLG register)

1 = Interrupt on EFLG error condition change

0 =Disabled

bit 4 TX2IE: Transmit Buffer 2 Empty Interrupt Enable bit

1 = Interrupt on TXB2 becoming empty

0 =Disabled

bit 3 TX1IE: Transmit Buffer 1 Empty Interrupt Enable bit

1 = Interrupt on TXB1 becoming empty

0 =Disabled

bit 2 TX0IE: Transmit Buffer 0 Empty Interrupt Enable bit

1 = Interrupt on TXB0 becoming empty

0 =Disabled

bit 1 RX1IE: Receive Buffer 1 Full Interrupt Enable bit

1 = Interrupt when message received in RXB1

0 =Disabled

bit 0 RX0IE: Receive Buffer 0 Full Interrupt Enable bit

1 = Interrupt when message received in RXB0

0 =Disabled

MCP2515

(ADDRESS: 2Ch)

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

MERRF WAKIF ERRIF TX2IF TX1IF TX0IF RX1IF RX0IF

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7 MERRF: Message Error Interrupt Flag bit

1 = Interrupt pending (must be cleared by MCU to reset interrupt condition)

0 = No interrupt pending

bit 6 WAKIF: Wakeup Interrupt Flag bit

1 = Interrupt pending (must be cleared by MCU to reset interrupt condition)

0 = No interrupt pending

bit 5 ERRIF: Error Interrupt Flag bit (multiple sources in EFLG register)

1 = Interrupt pending (must be cleared by MCU to reset interrupt condition)

0 = No interrupt pending

bit 4 TX2IF: Transmit Buffer 2 Empty Interrupt Flag bit

1 = Interrupt pending (must be cleared by MCU to reset interrupt condition)

0 = No interrupt pending

bit 3 TX1IF: Transmit Buffer 1 Empty Interrupt Flag bit

1 = Interrupt pending (must be cleared by MCU to reset interrupt condition)

0 = No interrupt pending

bit 2 TX0IF: Transmit Buffer 0 Empty Interrupt Flag bit

1 = Interrupt pending (must be cleared by MCU to reset interrupt condition)

0 = No interrupt pending

bit 1 RX1IF: Receive Buffer 1 Full Interrupt Flag bit

1 = Interrupt pending (must be cleared by MCU to reset interrupt condition)

0 = No interrupt pending

bit 0 RX0IF: Receive Buffer 0 Full Interrupt Flag bit

1 = Interrupt pending (must be cleared by MCU to reset interrupt condition)

0 = No interrupt pending

MCP2515

NOTES:

MCP2515

8.0 OSCILLATOR

The MCP2515 is designed to be operated with a crystal

or ceramic resonator connected to the OSC1 and

OSC2 pins. The MCP2515 oscillator design requires

the use of a parallel cut crystal. Use of a series cut

crystal may give a frequency out of the crystal

manufacturers specifications. A typical oscillator circuit

is shown in Figure 8-1. The MCP2515 may also be

driven by an external clock source connected to the

OSC1 pin, as sh ow n in Figure 8-2 and Figure 8-3.

8.1 Oscillator Startup Timer

The MCP2515 utilizes an Oscillator Startup Timer

(OST) that holds the MCP251 5 in reset to ensure that

the oscillator has stabilized before the internal state

machine begins to operate. The OST maintains reset

for the first 128 OSC1 clock cycles after power-up or a

wake-up from Sleep mode occurs. It should be noted

that no SPI protocol operations should be attempted

until after the OST has expired.

8.2 CLKOUT Pin

The CLKOUT pin is provided to the system designer for

use as the main system clock or as a clock input for

other devices in the system. The CLKOUT has an inter-

nal prescaler which can divid e FOSC by 1, 2, 4 and 8.

The CLKOUT function is ena bled and the prescaler is

selected via the CANCNTRL register (see

The CLKOUT pin will be active upon system reset and

default to the slowest speed (divide by 8) so that it can

be used as the MCU clock.

When Sleep mode is requested, the MCP2515 will

drive sixteen additional clock cycles on the CLKOUT

pin before entering Sleep mode. The idle state of the

CLKOUT pin in Sleep mode is low . When the CLKOUT

function is disabled (CANCNTRL.CLKEN = ‘0’) the

CLKOUT pin is in a high-impedance state.

The CLKOUT function is designed to ensure that

thCLKOUT and tlCLKOUT timings are preserved when the

CLKOUT pin function is enabled, disabled or the

prescaler value is changed.

FIGURE 8-1: CRYST AL/CERAMIC RESONATOR OPERATION

FIGURE 8-2: EXTERNAL CLOCK SOURCE

Note: The maximum frequency on CLKOUT is

specified as 25 MHz (See Table 13-5)

XTAL

OSC2

RS(1)

OSC1

RF(2) SLEEP

To internal logic

Note 1: A series resistor (RS) may be required for AT strip cut crystals.

2: The feedback resistor (RF), is typically in the range of 2 to 10 MΩ.

Clock from

external system OSC1

OSC2

Open

(1)

Note 1: A resistor to ground may be used to reduce system noise. This may increase system current.

2: Duty cycle restrictions must be observed (see Table 12-1).

MCP2515

FIGURE 8-3: EXTERNAL SERIES RESONANT CRYSTAL OSCILLATOR CIRCUIT(1)

TABLE 8-1: CAPACITOR SELECTION FOR

CERAMIC RESONATORS TABLE 8-2: CAPACITOR SELECTION FOR

CRYSTAL OSCILLATOR

330 kΩ

74AS04 74AS04 MCP2510

OSC1

To Other

Devices

XTAL

330 kΩ

74AS04

0.1 mF

Note 1: Duty cycle restrictions must be observed (see Table 12-1).

Typical Capacitor Values Used:

Mode Freq. OSC1 OSC2

HS 8.0 MHz 27 pF 27 pF

16.0 MHz 22 pF 22 pF

Capacitor values are for design guidance on ly:

These capacitors were tested with the resonators

listed below for basic start-up and operation. These

values are not optimized.

Different capacitor values may be required to

produce acceptable oscillator operation. The user

should test the performance of the oscillator over the

expected VDD and temperature range for the

application.

See the notes following Table 8-2 for additional infor-

mation. Resonators Used:

4.0 MHz

8.0 MHz

16.0 MHz

Osc

Type(1)(4) Crystal

Freq.(2)

Typical Capacitor

Valu es Tested:

C1 C2

HS 4 MHz 27 pF 27 pF

8 MHz 22 pF 22 pF

20MHz 15pF 15pF

Capacitor values are for design guidance only:

These capacitors were test ed with the crystals listed

below for basic start-up and operation. These values

are not optimized.

Different capacitor values may be required to

produce acceptable oscillator operation. The user

should test the performance of the oscillator over the

expected VDD and temp erature range for the

application.

See the notes following this Table for additional

information.

Crystals Used(3):

4.0 MHz

8.0 MHz

20.0 MHz

Note 1: While higher capacitance increases the

stability of the oscillator, it also increases

the start-up time.

2: Since each resonator/crystal has its own

characteristics, the user should consult

the resonator/crystal manufacturer for

appropriate values of external

components.

3: RS may be required to avoid overdriving

crystals with low drive level specification.

4: Always verify oscillator perfo rmanc e over

the VDD and temperature range that is

expected for the application.

MCP2515

9.0 RESET

The MCP2515 differentiates between two resets:

1. Hardware Reset – Low on RESET pin.

2. SPI Reset – Reset via SPI command.

Both of these resets are functionally equivalent. It is

important to provide one of these two resets after

power-up to ensure that the logic and registers are in

their default state. A hardware reset can be achieved

automatically by placing an RC on the RESET pin. (see

Figure 9-1). The values must be such that the device is

held in reset for a minimum of 2 µs after VDD reaches

operating voltage, as indicated in the electrical

specification (tRL).

FIGURE 9-1: RESET PIN CONFIGURATION EXAMPLE

RESET

R1(2)

VDD

D(1)

Note 1: The diode D helps discharge the capacitor quickly when VDD powers down.

2: R1 = 1 kΩ to 10 kΩ will limit any current flowing into RESET from external

capacitor C, in the event of RESET pin breakdown due to Electrostatic

Discharge (ESD) or Electrical Overstress (EOS).

MCP2515

NOTES:

MCP2515

10.0 MODES OF OPERATION

The MCP2515 has five modes of operation. These

modes are:

1. Configuration mode.

2. Normal mode.

3. Sleep mode.

4. Listen-only mode.

5. Loopback mode.

The operational mode is selected via the

CANCTRL. REQOP bits (see Register 10-1).

When changing modes, the mode will not actually

change until all pending message transmissions are

complete. The requested mode must be verified by

reading the CANSTAT.OPMODE bits (see

10.1 Configuration Mode

The MCP2515 must be initialized before activation.

This is only possible if the device is in the Configuration

mode. Configuration mode is automatically selected

after power-up, a reset or can be entered from any

other mode by setting the CANTRL.REQOP bits to

‘100’. When Configuration mode is entered, all error

counters are cleared. Configuration mode is the only

mode where the following registers are modifiable:

• CNF1, CNF2, CNF3

• TXRTSCTRL

• Filter registers

• Mask registers

10.2 Sleep Mode

The MCP2515 has an internal Sleep mode that is used

to minimize the current consumption of the device. The

SPI interface remains active for reading even when the

MCP2515 is in Sleep mode, allowing access to all

registers.

To enter Sleep mode, the mode re quest bits are set in

the CANCTRL register (REQOP<2:0>). The

CANSTAT.OPMODE bits indicate operation mode.

These bits should be read after sending the sleep

command to the MCP2515. The MCP2515 is active

and has not yet entered Sleep mode until these bits

indicate that Sleep mode has been entered.

When in intern al Sleep mode, the wake-up interrupt is

still active (if enabled). This is done so that the MCU

can also be placed into a Sleep mode and use the

MCP2515 to wake it up upon detecting activity on the

bus.

When in Sleep mode, the MCP2515 stops its internal

oscillator . The MCP2515 will wake-up when bus activity

occurs or when the MCU sets, via the SPI interface, the

CANINTF.WAKIF bit to ‘generate’ a wake-up attempt

(the CANINTE.WAKIE bit must also be set in order for

the wake-up interrupt to occur).

The TXCAN pin will remain in the recessive state while

the MCP2515 is in Sleep mode.

10.2.1 WAKE-UP FUNCTIONS

The device will monitor the RXCAN pin for activity while

it is in Sleep mode. If the CANINTE.WAKIE bit is set,

the device will wake up and generate an interrupt.

Since the internal oscillator is shut down while in Sleep

mode, it will take some amount of time for the oscillator

to start up and the device to enable itself to receive

messages. This Oscillator Start-up Timer (OST) is

defined as 128 TOSC.

The device will ignore the message that caused the

wake-up from Sleep mode, as well as any messages

that occur while the device is ‘waking up’. The device

will wake up in Listen-only mode. The MCU must set

Normal mode before the DSTEMP will be able to

communicate on th e bu s.

The device can be programmed to apply a low-pass

filter function to the RXCAN input line while in intern al

Sleep mode. This feature can be used to prevent the

device from waking up due to short glitches on the CAN

bus lines. The CNF3.WAKFIL bit enables or disables

the filter.

10.3 Listen-only Mode

Listen-only mode provides a means for the MCP2515

to receive all messages (including messages with

errors) by configuring the RXBnCTRL.RXM<1 :0> bits.

This mode can be used for bus monitor applications or

for detecting the baud rate in ‘hot plugging’ situations.

For auto-baud detection, it is necessary that there are

at least two other nodes that are communicating with

each other. The baud rate can be detected empirically

by testing different values until valid messages are

received.

Listen-only mode is a silent mode, meaning no

messages will be transmitted while in this mode

(including error flags or acknowledge signals). The

filters and masks can be used to allow only particular

messages to be loaded into the receive registers, or the

masks can be set to all zeros to allow a message with

any identifier to pass. The error counters are reset and

deactivated in this state. The Listen-only mode is

activated by setting the mode request bits in the

CANCTRL register.

MCP2515

10.4 Loopback Mode

Loopback mode will allow internal transmission of

messages from the transmit buffers to the receive

buffers without actually transmitting messages on the

CAN bus. This mode can be used in system

development and testing.

In this mode, the ACK bit is ignored and the device will

allow incoming messages from itself just as if they were

coming from another node. The Loopback mode is a

silent mode, meaning no messages will be transmitted

while in this state (including error flags or acknowledge

signals). The TXCAN pin will be in a recessive state.

The filters and masks can be used to allow only

particular messages to be loaded into the receive

registers. The masks can be set to all zeros to provide

a mode that accepts all messages. The Loopback

mode is activated by setting the mode request bits in

the CANCTRL register.

10.5 Normal Mode

Normal mode is the standard operating mode of the

MCP2515. In this mode, the device actively monitors all

bus messages and g enerates acknowledge bits, error

frames, etc. This is also the only mode in which the

MCP2515 will transmit messages over the CAN bus.

(ADDRESS: XFh)

R/W-1 R/W-0 R/W-0 R/W-0 R/W-0 R/W-1 R/W-1 R/W-1

REQOP2 REQOP1 REQOP0 ABAT OSM CLKEN CLKPRE1 CLKPRE0

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-5 REQOP: Request Operation Mode bits <2:0>

000 = Set Normal Operation mode

001 = Set Sleep mode

010 = Set Loopback mode

011 = Set Listen-o n ly mode

100 = Set Configuration mode

All other values for REQOP bits are invalid and should not be used

On power-up, REQOP = b’111’

bit 4 ABAT: Abort All Pending Transmissions bit

1 = Request abort of all pending transmit buffers

0 = Terminate request to abort all transmissions

bit 3 OSM: One Shot Mode bit

1 = Enabled. Message will only attempt to transmit one time

0 = Disabled. Messages will reattempt transmission, if required

bit 2 CLKEN: CLKOUT Pin Enable bit

1 = CLKOUT pin enabled

0 = CLKOUT pin disabled (Pin is in high-impedance state)

bit 1-0 CLKPRE: CLKOUT Pin Prescaler bits <1:0>

00 =F

CLKOUT = System Clock/1

01 =F

CLKOUT = System Clock/2

10 =F

CLKOUT = System Clock/4

11 =F

CLKOUT = System Clock/8

MCP2515

(ADDRESS: XEh)

R-1 R-0 R-0 U-0 R-0 R-0 R-0 U-0

OPMOD2 OPMOD1 OPMOD0 — ICOD2 ICOD1 ICOD0 —

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 7-5 OPMOD: Operation Mode bits <2:0>

000 = Device is in the Normal operation mode

001 = Device is in Sleep mode

010 = Device is in Loopback mode

011 = Device is in Listen-only mode

100 = Device is in Configuration mode

bit 4 Unimplemented: Read as ‘0’

bit 3-1 ICOD: Interrupt Flag Code bits <2:0>

000 = No Interrupt

001 = Error Interrupt

010 = Wake-up Interrupt

011 = TXB0 Interrupt

100 = TXB1 Interrupt

101 = TXB2 Interrupt

110 = RXB0 Interrupt

111 = RXB1 Interrupt

bit 0 Unimplemented: Read as ‘0’

MCP2515

NOTES:

MCP2515

11.0 REGISTER MAP

The register map for the MCP2515 is shown in

Table 11-1. Address locations for each register are

determined by using the column (higher-order 4 bits)

and row (lower-order 4 bits) values. The registers

have been arranged to optimize the sequential

reading and writing of dat a. Some specific control and

status registers allow individual bit modification using

the SPI Bit Modify command. The registers that allow

this command are shown as shaded locations in

Table 11-1. A summary of the MCP2515 control

registers is shown in Table 11-2.

TABLE 11-1: CAN CONTROLLER REGISTER MAP

TABLE 11-2: CONTROL REGISTER SUMMARY

Lower

Address

Bits

Higher-Order Address Bits

0000 xxxx 0001 xxxx 0010 xxxx 0011 xxxx 0100 xxxx 0101 xxxx 0110 xxxx 0111 xxxx

0000 RXF0SIDH RXF3SIDH RXM0SIDH TXB0CTRL TXB1CTRL TXB2CTRL RXB0CTRL RXB1CTRL

0001 RXF0SIDL RXF3SIDL RXM0SIDL TXB0SIDH TXB1SIDH TXB2SIDH RXB0SIDH RXB1SIDH

0010 RXF0EID8 RXF3EID8 RXM0EID8 TXB0SIDL TXB1SIDL TXB2SIDL RXB0SIDL RXB1SIDL

0011 RXF0EID0 RXF3EID0 RXM0EID0 TXB0EID8 TXB1EID8 TXB2EID8 RXB0EID8 RXB1EID8

0100 RXF1SIDH RXF4SIDH RXM1SIDH TXB0EID0 TXB1EID0 TXB2EID0 RXB0EID0 RXB1EID0

0101 RXF1SIDL RXF4SIDL RXM1SIDL TXB0DLC TXB1DLC TXB2DLC RXB0DLC RXB1DLC

0110 RXF1EID8 RXF4EID8 RXM1EID8 TXB0D0 TXB1D0 TXB2D0 RXB0D0 RXB1D0

0111 RXF1EID0 RXF4EID0 RXM1EID0 TXB0D1 TXB1D1 TXB2D1 RXB0D1 RXB1D1

1000 RXF2SIDH RXF5SIDH CNF3 TXB0D2 TXB1D2 TXB2D2 RXB0D2 RXB1D2

1001 RXF2SIDL RXF5SIDL CNF2 TXB0D3 TXB1D3 TXB2D3 RXB0D3 RXB1D3

1010 RXF2EID8 RXF5EID8 CNF1 TXB0D4 TXB1D4 TXB2D4 RXB0D4 RXB1D4

1011 RXF2EID0 RXF5EID0 CANINTE TXB0D5 TXB1D5 TXB2D5 RXB0D5 RXB1D5

1100 BFPCTRL TEC CANINTF TXB0D6 TXB1D6 TXB2D6 RXB0D6 RXB1D6

1101 TXRTSCTRL REC EFLG TXB0D7 TXB1D7 TXB2D7 RXB0D7 RXB1D7

1110 CANSTAT CANSTAT CANSTAT CANSTAT CANSTAT CANSTAT CANSTAT CANSTAT

1111 CANCTRL CANCTRL CANCTRL CANCTRL CANCTRL CANCTRL CANCTRL CANCTRL

Note: Shaded register locations indicate that these allow the user to manipulate individual bits using the Bit Modify command.

Name Address

(Hex) Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 POR/RST

Value

BFPCTRL 0C — — B1BFS B0BFS B1BFE B0BFE B1BFM B0BFM --00 0000

TXRTSCTRL 0D — — B2RTS B1RTS B0RTS B2RTSM B1RTSM B0RTSM --xx x000

CANSTAT xE OPMOD2 OPMOD1 OPMOD0 — ICOD2 ICOD1 ICOD0 — 100- 000-

CANCTRL xF REQOP2 REQOP1 REQOP0 ABAT OSM CLKEN CLKPRE1 CLKPRE0 1110 0111

TEC 1C Transmit Error Counter (TEC) 0000 0000

REC 1D Receive Error Counter (REC) 0000 0000

CNF3 28 SOF WAKFIL — — — PHSEG22 PHSEG21 PHSEG20 00-- -000

CNF2 29 BTLMODE SAM PHSEG12 PHSEG11 PHSEG10 PRSEG2 PRSEG1 PRSEG0 0000 0000

CNF1 2A SJW1 SJW0 BRP5 BRP4 BRP3 BRP2 BRP1 BRP0 0000 0000

CANINTE 2B MERRE WAKIE ERRIE TX2IE TX1IE TX0IE RX1IE RX0IE 0000 0000

CANINTF 2C MERRF WAKIF ERRIF TX2IF TX1IF TX0IF RX1IF RX0IF 0000 0000

EFLG 2D RX1OVR RX0OVR TXBO TXEP RXEP TXWAR RXWAR EWARN 0000 0000

TXB0CTRL 30 — ABTF MLOA TXERR TXREQ — TXP1 TXP0 -000 0-00

TXB1CTRL 40 — ABTF MLOA TXERR TXREQ — TXP1 TXP0 -000 0-00

TXB2CTRL 50 — ABTF MLOA TXERR TXREQ — TXP1 TXP0 -000 0-00

RXB0CTRL 60 — RXM1 RXM0 — RXRTR BUKT BUKT FILHIT0 -00- 0000

RXB1CTRL 70 — RSM1 RXM0 — RXRTR FILHIT2 FILHIT1 FILHIT0 -00- 0000

MCP2515

NOTES:

MCP2515

12.0 SPI INTERFACE

12.1 Overview

The MCP2515 is designed to interface directly with the

Serial Peripheral Interface (SPI) port available on many

microcontrollers and supports Mode 0,0 and Mode 1,1.

Commands and data are sent to the device via the SI

pin, with data being clocked in on the rising edge of

SCK. Data is driven out by the MCP2515 (on the SO

line) on the falling edge of SCK. The CS pin must be

held low while a ny operation is performed. Table 12-1

shows the instruction bytes for al l operations. Refer to

Figure 12-10 and Figure 12-11 for detailed input and

output timing diagrams for both Mode 0,0 and Mode 1,1

operation.

12.2 Reset Instruction

The Reset instruction can be used to re-initialize the

internal registers of the MCP2515 and set Configuration

mode. This command provides the same functionality,

via the SPI interface, as th e R ESET pi n.

The Reset instruction is a single-byte instruction that

requires selecting the device by pulling CS low,

sending the instruction byte and then raising CS. It is

highly recommended that the reset command be sent

(or the RESET pin be lowered) as part of the power-on

initialization sequence.

12.3 Read Instruction

The Read instruction is started by lowering the CS pin.

The Read instruction is then sent to the MCP2515

followed by the 8-bit address (A7 through A0). Next, the

data stored in the register at the selected address will

be shifted out on the SO pin.

The internal address pointer is automatically

incremented to the next address once each byte of

data is shifted out. Therefore, it is possible to read the

next consecutive register address by continuing to pro-

vide clock pulses. Any number of consecutive register

locations can be read sequentially using this method.

The read operation is terminated by raisin g the CS pi n

(Figure 12-2).

12.4 Read RX Buffer Instruction

The Read RX Buffer instruction (Figure 12-3) provides

a means to quickly address a receive buffer for reading.

This instruction reduces the SPI overhead by one byte,

the address byte. The command byte actually has four

possible values that determine the address pointer

location. Once the command byte is sent, the controller

clocks out the data at the address location the same as

the Read instruction (i.e., sequential reads are

possible). This instruction further reduces the SPI

overhead by automatically clearing the associated

receive flag (CANINTF.RXnIF) when CS is raised at the

end of the command.

12.5 Write Instruction

The Write instruction is started by lowering the CS pin.

The Write instruction is then sent to the MCP2515

followed by the address and at least one byte of data.

It is possible to write to sequential registers by

continuing to clock in data bytes, as long as CS is held

low. Data will actually be written to th e register on the

rising edge of the SCK line for the D0 bit. If the CS line

is brought high before eight bits are loaded, the write

will be aborted for that data byte and previou s byte s in

the command will have been written. Refer to the timing

diagram in Figure 12-4 for a more detailed illustration of

the byte write sequence.

12.6 Load TX Buffer Instruction

The Load TX Buffer instruction (Figure 12-5) eliminates

the eight-bit address required by a normal write

command. The eight-bit instruction sets the address

pointer to one of six addresses to quickly write to a

transmit buffer that points to the “ID” or “data” address

of any of the three transmit buffers.

12.7 Request-To-Send (RTS)

Instruction

The RTS command can be used to initiate message

transmission for one or more of the transmit buffers.

The MCP2515 is selected by lowering the CS pin. The

RTS command byte is then sent. Shown in Figure 12-6,

the last 3 bits of this command indicate which transmit

buffer(s) are enable d to send.

This command will set the TxBnCTRL.TXREQ bit for

the respective buffer(s). Any or all of the last thre e bi ts

can be set in a single command. If the RTS command

is sent with nnn = 000, the command will be ignored.

12.8 Read Status Instruction

The Read Status instruction allows single instruction

access to some of the often used status bits for

message reception and transmission.

The MCP2515 is selected by lowering the CS pin and

the read status command byte, shown in Figure 12-8,

is sent to the MCP2515. Once the command byte is

sent, the MCP2515 will return eight bits of data that

contain the status.

If additional clocks are sent after the first eight bits are

transmitted, the MCP2515 will continue to output the

status bits as long as the CS pin is held low and clocks

are provided on SCK.

Note: The MCP2515 expects the first byte after

lowering CS to be the instruction/

command byte. This implies that CS must

be raised and then lowered again to

invoke another command.

MCP2515

Each status bit returned in this command may also be

read by using the standard read command with the

appropriate register address.

12.9 RX Status Instruction

The RX Status instruction (Figure 12-9) is used to

quickly determine which filter matched the message

and message type (standard, exten ded, remote). After

the command byte is sent, the controller will return

8 bits of data that contain the status data. If more clocks

are sent after the 8 bits are transmitted, the controller

will continue to output the sa me status bits as long as

the CS pin stays low and clocks are provided.

12.10 Bit Modify Instruction

The Bit Modify instruction provides a means for setting

or clearing individual bits in specific status and control

registers. This command is not available for all

registers. See Section 11.0 “Register Map” to

determine which registers allow the use of this

command.

The part is selected by lowering the CS pin and the Bit

Modify command byte is then sent to the MCP2515.

The command is followed by the address of the

The mask byte determines which bits in the register will

be allowed to chang e. A ‘1’ in the ma sk byte will allow

a bit in the register to change, while a ‘0’ will not.

The data byte determines what value the modified bits

in the register will be changed to. A ‘1’ in the data byte

will set the bit and a ‘0’ will clear th e bit, provided that

the mask for that bit is set to a ‘1’ (see Figure 12-7).

FIGURE 12-1: BIT MODIFY

TABLE 12-1: SPI INSTRUCTION SET

Note: Executing the Bit Modify command on

registers that are not bit-modifiable will

force the mask to FFh. This will allow byte-

writes to the registers, not bit modify.

Mask byte

Data byte

Contents

Resulting

Contents

001 11100

XX1 100XX

010 11000

011 10000

Instruction Name Instruction Format Description

RESET 1100 0000 Resets internal registers to default state, set Configuration mode.

READ 0000 0011 Read data from register beginning at selected address.

Read RX Buffer 1001 0nm0 When read ing a receive buffer, reduces the overhead of a normal

read command by placing the address pointer at one of four

locations, as indicated by ‘n,m’. Note: The associated RX flag bit

(CANINTF.RXnIF) will be cleared after bringing CS high.

WRITE 0000 0010 Write data to register beginning at selected address.

Load TX Buffer 0100 0abc When loading a transmit buffer, reduces the overhead of a normal

Write command by placing the address pointer at one of six

locations as indicated by ‘a,b,c’.

RTS

(Message

Request-To-Send)

1000 0nnn Instructs controller to begin message transmission sequence for

any of the transmit buffers.

Read Status 1010 0000 Quick polling command that reads several status bits for transmit

and receive functions.

RX Status 1011 0000 Quick polling command that indicates fil te r match and message

type (standard, extended and/or remote) of received message.

Bit Modify 0000 0101 Allows the user to set or clear individual bits in a particular

command. Executing this command on registers that are not bit-

modifiable will force the mask to FFh. See the register map in

Section 11.0 “Register Map” for a list of the registers that apply.

1000 0nnn Request-to-send for TXBO

Request-to-send for TXB1

Request-to-send for TXB2

MCP2515

FIGURE 12-2: READ INSTRU CTION

FIGURE 12-3: READ RX BUFFER INSTRUCTION

FIGURE 12-4: BYTE W RITE INSTRUCTION

SCK

0 23456789101112131415161718192021221

01000001

A7 6 5 4 1A0

76543210

instruction address byte

data out

high-impedance

32 don’t care

SCK

0 234567891011121314151

76543210

instruction

data out

high-impedance

don’t care

n m Address Points to Address

00Receive Buffer 0,

Start at RXB0SIDH 0x61

01Receive Buffer 0,

Start at RXB0D0 0x66

10Receive Buffer 1,

Start at RXB1SIDH 0x71

11Receive Buffer 1,

Start at RXB1D0 0x76

01001

SCK

0 2 3 4 5 6 7 8 9101112131415161718192021221

0000000 A7 6 5 4 1A076543210

instruction

high-impedance

address byte data byte

MCP2515

FIGURE 12-5: LOAD TX BUFFER

FIGURE 12-6: REQUEST-TO-SEND (RTS) INSTRUCTION

FIGURE 12-7: BIT MODIFY INSTRUCTION

SCK

0 234567891011121314151

ac00010b

76543210

instruction data in

high-impedance

a b c Address Points to Addr

000TX buffer 0, Start at

TXB0SIDH 0x31

001TX buffer 0, Start at

TXB0D0 0x36

010TX buffer 1, Start at

TXB1SIDH 0x41

011TX buffer 1, Start at

TXB1D0 0x46

100TX buffer 2, Start at

TXB2SIDH 0x51

101TX buffer 2, Start at

TXB2D0 0x56

SCK

0 2345671

T2 T000

instruction

high-impedance

SCK

0 23456789101112131415161718192021221

1100000 A7 6 5 4 1A0 76543210

instruction

high-impedance

address byte mask byte

76543210

23 24 25 26 27 28 2930 31

data byte

Note: Not all registers can be accessed with

this command. See the register map for a

list of the registers that apply.

MCP2515

FIGURE 12-8: READ S TATUS INSTRUCTION

FIGURE 12-9: RX S TATUS INSTRUCTION

SCK

0 23456789101112131415161718192021221

00001010

76543210

instruction

data out

high-impedance

don’t care

CANINTF.RX0IF

CANINTFL.RX1IF

CANINTF.TX0IF

CANINTF.TX1IF

CANINTF.TX2IF

TXB2CNTRL.TXREQ

TXB1CNTRL.TXREQ

TXB0CNTRL.TXREQ

76543210

data out

repeat

SCK

0 23456789101112131415161718192021221

00011010

76543210

instruction

data out

high-impedance

don’t care

76543210

data out

repeat

2 1 0 Filter Match

000RXF0

001RXF1

010RXF2

011RXF3

100RXF4

101RXF5

110RXF0 (rollover to RXB1)

111RXF1 (rollover to RXB1)

CANINTF.RXnIF bits are mapped to

bits 7 and 6.

7 6 Receiv ed Message

00No RX message

01Message in RXB0

10Message in RXB1

11Messages in both bu f fers* The extended ID bit is mapped to

bit 4. The RTR bit is mapped to

bit 3.

4 3 Msg Type Received

00Standard data frame

01Standard remote frame

10Extended data frame

11Extended remote frame

* Buffer 0 has higher priority, therefore, RXB0 status is

reflected in bits 4:0.

MCP2515

FIGURE 12-10: SPI INPUT TIMING

FIGURE 12-11: SPI OUTPUT TIMING

SCK

LSB in

MSB in

high-impedance

Mode 1,1

Mode 0,0

SCK

MSB out LSB out

don’t care

Mode 1,1

Mode 0,0

MCP2515

13.0 ELECTRICAL CHARACTERISTICS

13.1 Absolute Maximum Ratings †

VDD.............................................................................................................................................................................7.0V

All inputs and outputs w.r.t. VSS ................ ... .................... ................... ... .................... ................... ... ...-0.6V to VDD +1.0V

Storage temperature ...............................................................................................................................-65°C to +150°C

Ambient temp. with power applied........................ ..................................................................................-65°C to +125°C

Soldering temperature of leads (10 seconds).......................................................................................................+300°C

† Notice: Stresses above those listed under “Maximum Ratings” may caus e permanent damage to the d evice. This

is a stress rating only and functional operation of the device at those or any other conditions above those indicated in

the operational listings of this specification is not implied. Exposure to maximum rating conditions for extended periods

may affect device reliability.

MCP2515

TABLE 13-1: DC CHARACTERISTICS

DC Characteristics Industrial (I): TAMB = -40°C to +85°C VDD = 2.7V to 5.5V

Extended (E): TAMB = -40°C to +125°C VDD = 4.5V to 5.5V

Param.

No. Sym Characteristic Min Max Units Conditions

VDD Supply Voltage 2.7 5.5 V

VRET Register Retention Voltage 2.4 — V

High-Level Input Voltage

VIH RXCAN 2 VDD + 1 V

SCK, CS, SI, TXnRTS Pins 0.7 VDD VDD + 1 V

OSC1 0.85 VDD VDD V

RESET 0.85 VDD VDD V

Low-Level Input Voltage

VIL RXCAN, TXnRTS Pins -0.3 .15 VDD V

SCK, CS, SI -0.3 0.4 V

OSC1 VSS .3 VDD V

RESET VSS .15 VDD V

Low-Level Output Voltage

VOL TXCAN — 0.6 V IOL = +6.0 mA, VDD = 4.5V

RXnBF Pins — 0.6 V IOL = +8.5 mA, VDD = 4.5V

SO, CLKOUT — 0.6 V IOL = +2.1 mA, VDD = 4.5V

INT —0.6VIOL = +1.6 mA, VDD = 4.5V

High-Level Output Voltage V

VOH TXCAN, RXnBF Pins VDD – 0.7 — V IOH = -3.0 mA, VDD = 4.5V

SO, CLKOUT VDD – 0.5 — V IOH = -400 µA, VDD = 4.5V

INT VDD – 0.7 — V IOH = -1.0 mA, VDD = 4.5V

Input Leakage Current

ILI All I/O except OSC1 and

TXnRTS pins -1 +1 µA CS = RESET = VDD,

VIN = VSS to VDD

OSC1 Pin -5 +5 µA

CINT Internal Capacitance

(All Inputs and Outputs) —7pFTAMB = 25°C, fC = 1.0 MHz,

VDD = 0V (Note 1)

IDD Operating Current — 10 mA VDD = 5.5V, FOSC = 25 MHz,

FCLK = 1 MHz, SO = Open

IDDS Standby Current (Sleep mode) — 5 µA CS, TXnRTS = VDD, Inputs tied to

VDD or VSS, -40°C TO +85°C

—8µACS,

TXnRTS = VDD, Inputs tied to

VDD or VSS, -40°C TO +125°C

Note 1: This parameter is periodically sampled and not 100% tested.

MCP2515

TABLE 13-2: OSCILLATOR TIMING CHARACTERISTICS

TABLE 13-3: CAN INTERFACE AC CHARACTERISTICS

TABLE 13-4: RESET AC CHARACTERISTICS

Oscillator Timing Characteristics(Note) Industrial (I): TAMB = -40°C to +85°C VDD = 2.7V to 5.5V

Extended (E): TAMB = -40°C to +125°C VDD = 4.5V to 5.5V

Param.

No. Sym Characteristic Min Max Units Conditions

FOSC Clock-In Frequency 1

140

25 MHz

MHz 4.5V to 5.5V

2.7V to 5.5V

TOSC Clock-In Period 25

40 1000

1000 ns

ns 4.5V to 5.5V

2.7V to 5.5V

TDUTY Duty Cycle

(External Clock Input) 0.45 0.55 — TOSH/(TOSH + TOSL)

Note: This parameter is periodically sampled and not 100% tested.

CAN Interface AC Characteristics Industrial (I): TAMB = -40°C to +85°C VDD = 2.7V to 5.5V

Extended (E): TAMB = -40°C to +125°C VDD = 4.5V to 5.5V

Param.

No. Sym Characteristic Min Max Units Conditions

TWF Wake-up Noise Filter 100 — ns

RESET AC Characteristics Industrial (I): TAMB = -40°C to +85°C VDD = 2.7V to 5.5V

Extended (E): TAMB = -40°C to +125°C VDD = 4.5V to 5.5V

Param.

No. Sym Characteristic Min Max Units Conditions

trl RESET Pin Low Time 2 — µs

MCP2515

TABLE 13-5: CLKOUT PIN AC CHARACTERISTICS

FIGURE 13-1: S T ART-OF-FRAME PIN AC CHARACTERISTICS

CLKOUT Pin AC/DC Characteristics Industrial (I): TAMB = -40°C to +85°C VDD = 2.7V to 5.5V

Extended (E): TAMB = -40°C to +125°C VDD = 4.5V to 5.5V

Param.

No. Sym Characteristic Min Max Units Conditions

thCLKOUT CLKOUT Pin High Time 15 — ns TOSC = 40 ns (Note 1)

tlCLKOUT CLKOUT Pin Low Time 15 — ns TOSC = 40 ns (Note 1)

trCLKOUT CLKOUT Pin Rise Time — 5 ns Measured from 0.3 VDD to 0.7 VDD

(Note 1)

tfCLKOUT CLKOUT Pin Fall Time — 5 ns Measured from 0.7 VDD to 0.3 VDD

(Note 1)

tdCLKOUT CLOCKOUT Propagation Delay — 100 ns Note 1

15 thSOF Start-Of-Frame High Time — 2 TOSC ns Note 1

16 tdSOF Start-Of-Frame Propagation

Delay —2TOSC +

0.5 TQns Measured from CAN bit sample

point. Device is a receiver.

CNF1.BRP<5:0> = 0 (Note 2)

Note 1: All CLKOUT mode functionality and output frequency is tested at device frequency limits, however , CLKOUT prescaler

is set to divide by one. This parameter is periodically sampled and not 100% tested.

2: Design guidance only, not tested.

RXCAN 16

sample point

MCP2515

TABLE 13-6: SPI INTERFACE AC CHARACTERISTICS

SPI Interface AC Characteristics In dustrial (I): TAMB = -40°C to +85°C VDD = 2.7V to 5.5V

Extended (E): TAMB = -40°C to +125°C VDD = 4.5V to 5.5V

Param.

No. Sym Characteristic Min Max Units Conditions

FCLK Clock Frequency — 10 MHz

CSS CS Setup Time 50 — ns

CSH CS Hold Time 50 — ns

CSD CS Disable Time 50 — ns

SU Data Setup Time 10 — ns

HD Data Hold Ti me 10 — ns

RCLK Rise Time — 2 µs Note 1

FCLK Fall Time — 2 µs Note 1

HI Clock High Time 45 — ns

LO Clock Low Time 45 — ns

10 TCLD Clock Delay Time 50 — ns

11 TCLE Clock Enable Time 50 — ns

12 TVOutput Valid from Clock Low — 45 ns

13 THO Output Hold Time 0 — ns

14 TDIS Output Disable Time — 100 ns

Note 1: This parameter is not 100% tested.

MCP2515

NOTES:

MCP2515

14.0 PACKAGING INFORMATION

14.1 Package Marking Information

18-Lead PDIP (300 mil)

18-Lead SOIC (300 mil)

20-Lead TSSOP (4.4 mm)

XXXXXXXX

XXXXXNNN

YYWW

XXXXXXXXXXXX

YYWWNNN

XXXXXXXXXXXXXXXXX

YYWWNNN

Example:

MCP2515

IST ^ 256

0434

MCP2515

0434256

MCP2515-I/P^^

0434256

Legend: XX...X Customer-specific information

Y Year code (last digit of calendar year)

YY Year code (last 2 digits of calendar year)

WW Week code (week of January 1 is week ‘01’)

NNN Alphanumeric traceability code

Pb-free JEDEC designator for Ma tte Tin (Sn)

*This package is Pb-free. The Pb-free JEDEC designator ( )

can be found on the outer packaging for this package.

Note: In the event the full Microchip part number cannot be marked on one line, it will

be carried over to the next line, thus limiting the number of available

characters for customer-specific information.

E/SO^^

MCP2515

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MCP2515

/HDG3ODVWLF6PDOO2XWOLQH62±:LGHPP%RG\>62,&@

1RWHV

 3LQYLVXDOLQGH[IHDWXUHPD\YDU\EXWPXVWEHORFDWHGZLWKLQWKHKDWFKHGDUHD

 6LJQLILFDQW&KDUDFWHULVWLF

 'LPHQVLRQV'DQG(GRQRWLQFOXGHPROGIODVKRUSURWUXVLRQV0ROGIODVKRUSURWUXVLRQVVKDOOQRWH[FHHGPPSHUVLGH

 'LPHQVLRQLQJDQGWROHUDQFLQJSHU$60(<0

%6& %DVLF'LPHQVLRQ7KHRUHWLFDOO\H[DFWYDOXHVKRZQZLWKRXWWROHUDQFHV

5() 5HIHUHQFH'LPHQVLRQXVXDOO\ZLWKRXWWROHUDQFHIRULQIRUPDWLRQSXUSRVHVRQO\

1RWH )RUWKHPRVWFXUUHQWSDFNDJHGUDZLQJVSOHDVHVHHWKH0LFURFKLS3DFNDJLQJ6SHFLILFDWLRQORFDWHGDW

KWWSZZZPLFURFKLSFRPSDFNDJLQJ

8QLWV 0,//,0(7(56

'LPHQVLRQ/LPLWV 0,1 120 0$;

1XPEHURI3LQV 1 

3LWFK H %6&

2YHUDOO+HLJKW $ ± ± 

0ROGHG3DFNDJH7KLFNQHVV $  ± ±

6WDQGRII $  ± 

2YHUDOO:LGWK ( %6&

0ROGHG3DFNDJH:LGWK ( %6&

2YHUDOO/HQJWK ' %6&

&KDPIHURSWLRQDO K  ± 

)RRW/HQJWK /  ± 

)RRWSULQW / 5()

)RRW$QJOH  ± 

/HDG7KLFNQHVV F  ± 

/HDG:LGWK E  ± 

0ROG'UDIW$QJOH7RS  ± 

0ROG'UDIW$QJOH%RWWRP  ± 

NOTE 1

123

0LFURFKLS 7HFKQRORJ\ 'UDZLQJ &%

MCP2515

/HDG3ODVWLF7KLQ6KULQN6PDOO2XWOLQH67±PP%RG\>76623@

1RWHV

 3LQYLVXDOLQGH[IHDWXUHPD\YDU\EXWPXVWEHORFDWHGZLWKLQWKHKDWFKHGDUHD

 'LPHQVLRQV'DQG(GRQRWLQFOXGHPROGIODVKRUSURWUXVLRQV0ROGIODVKRUSURWUXVLRQVVKDOOQRWH[FHHGPPSHUVLGH

 'LPHQVLRQLQJDQGWROHUDQFLQJSHU$60(<0

%6& %DVLF'LPHQVLRQ7KHRUHWLFDOO\H[DFWYDOXHVKRZQZLWKRXWWROHUDQFHV

5() 5HIHUHQFH'LPHQVLRQXVXDOO\ZLWKRXWWROHUDQFHIRULQIRUPDWLRQSXUSRVHVRQO\

1RWH )RUWKHPRVWFXUUHQWSDFNDJHGUDZLQJVSOHDVHVHHWKH0LFURFKLS3DFNDJLQJ6SHFLILFDWLRQORFDWHGDW

KWWSZZZPLFURFKLSFRPSDFNDJLQJ

8QLWV 0,//,0(7(56

'LPHQVLRQ/LPLWV 0,1 120 0$;

1XPEHURI3LQV 1 

3LWFK H %6&

2YHUDOO+HLJKW $ ± ± 

0ROGHG3DFNDJH7KLFNQHVV $   

6WDQGRII $  ± 

2YHUDOO:LGWK ( %6&

0ROGHG3DFNDJH:LGWK (   

0ROGHG3DFNDJH/HQJWK '   

)RRW/HQJWK /   

)RRWSULQW / 5()

)RRW$QJOH  ± 

/HDG7KLFNQHVV F  ± 

/HDG:LGWK E  ± 

NOTE 1

L1 L

0LFURFKLS 7HFKQRORJ\ 'UDZLQJ &%

MCP2515

APPENDIX A: REVISION HISTORY

Revision E (November 2007)

• Removed preliminary watermark.

• Updated templates.

• Updated register information.

• Updated package ou tl i ne drawings.

Revision D (April 2005)

• Added Table 8-1 and Table 8-2 in Section 8.0

“Oscillator”. Added note box following tables.

• Changed address bits in column heading in

Table 11-1, Section 11.0 “Register Map”.

• Modified Section 14.0 “Packaging Information”

to reflect pb free device marki ngs.

• Appendix A Revision History: Rearranged order of

importance.

Revision C (November 2004)

•Section 9.0 “RESET” added.

• Heading 12.1: added notebox.

Heading 12.6: Changed verbia ge within

paragraph in Section 12.0 “SPI Interface”.

• Added Appendix A: Revision History.

Revision B (September 2003)

• Front page bullet: S t andby current (typical) (Sleep

Mode) changed from 10 µA to 1 µA.

• Added notebox for maximum frequency on CLK-

OUT in Section 8.2 “CLKOUT Pin”.

•Section 12.0 “SPI Interface”, Table 12-1:

- Changed supply voltage minimum to 2.7V.

- Internal Capacitance: Changed VDD condition

to 0V.

- Standby Current (Sleep mode): Split

specification into -40°C to +85°C and

-40°C to +125°C.

Revision A (May 2003)

• Original Relase of this Document.

MCP2515

NOTES:

MCP2515

PRODUCT IDENTIFICATION SYSTEM

To order or obtain information, e.g., on pricing or delivery, refer to the factory or the listed sales office.

Device MCP2515: CAN Controller w/ SPI Interface

MCP2515T: CAN Controller w/SPI Interface

(Tape and Reel)

Temperature

Range I= -40°C to +85°C (Industrial)

E= -40°C to +125°C (Extended)

Package P = Plastic DIP (300 mil Body), 18-Lead

SO = Plastic SOIC (300 mil Body), 18-Lead

ST = TSSOP, (4.4 mm Body), 20-Lead

PART NO. X/XX

PackageTemperature

Range

Device

Examples:

a) MCP2515-E/P: Extended Temperature,

18LD PDIP package.

b) MCP2515-I/P: Industrial Temperature,

18LD PDIP package.

c) MCP2515-E/SO: Extended Temperature,

18LD SOIC package.

d) MCP2515-I/SO: Industrial Temperature,

18LD SOIC package.

e) MCP2515T-I/SO:Tape and Reel,

Industrial Temperature,

18LD SOIC package.

f) MCP2515-I/ST: Industrial Temperature,

20LD TSSOP package.

g) MCP2515T-I/ST: Tape and Reel,

Industrial Temperature,

20LD TSSOP package.

–

MCP2515

NOTES:

Information contained in this publication regarding device

applications and the like is provided only for your convenience

and may be superseded by updates. It is your responsibility to

ensure that your application meets with your specifications.

MICROCHIP MAKES NO REPRESENTATIONS OR

WARRANTIES OF ANY KIND WHETHER EXPRESS OR

IMPLIED, WRITTEN OR ORAL, STATUTORY OR

OTHERWISE, RELATED TO THE INFORMATION,

INCLUDING BUT NOT LIMITED TO ITS CONDITION,

QUALITY, PERFORMANCE, MERCHANTABILITY OR

FITNESS FOR PURPOSE. Microchip disclaims all liability

arising from this information and its use. Use of Microchip

devices in life support and/or safety applications is entirely at

the buyer’s risk, and the buyer agrees to defen d, indemnify and

hold harmless Microchip from any and all damages, claims,

suits, or expenses resulting from such use. No licenses are

conveyed, implicitly or otherwise, under any Microchip

intellectual property rights.

Trademarks

The Microchip name and logo, the Microchip logo, Accuron,

dsPIC, KEELOQ, KEELOQ logo, microID, MPLAB, PIC,

PICmicro, PICST ART, PRO MA TE, rfPIC and SmartShunt are

registered trademarks of Microchip Technology Incorporated

in the U.S.A. and other countries.

AmpLab, FilterLab, Linear Active Thermistor, Migratable

Memory, MXDEV, MXLAB, SEEVAL, SmartSensor and The

Embedded Control Solutions Company are registered

trademarks of Microchip Technology Incorporated in the

U.S.A.

Analog-for-the-Digital Age, Application Maestro, CodeGuard,

dsPICDEM, dsPICDEM.net, dsPICworks, dsSPEAK, ECAN,

ECONOMONITOR, FanSense, FlexROM, fuzzyLAB,

In-Circuit Serial Programming, ICSP, ICEPIC, Mindi, MiWi,

MPASM, MPLAB Certified logo, MPLIB, MPLINK, PICkit,

PICDEM, PICDEM.net, PICLAB, PICtail, PowerCal,

PowerInfo, PowerMate, PowerTool, REAL ICE, rfLAB, Select

Mode, Smart Serial, SmartTel, Total Endurance, UNI/O,

WiperLock and ZENA are trademarks of Microchip

Technology Incorporated in the U.S.A. and other countries.

SQTP is a service mark of Microchip T echnology Incorporated

in the U.S.A.

All other trademarks mentioned herein are property of their

respective companies.

Printed on recycled paper.

Note the following details of the code protection feature on Microchip devices:

• Microchip products meet the specification contained in their particular Microchip Data Sheet.

• Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the

intended manner and under normal conditions.

• There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our

knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Dat a

Sheets. Most likely, the person doing so is engaged in theft of intellectual property.

• Microchip is willing to work with the customer who is concerned about the integrity of their code.

• Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not

mean that we are guaranteeing the product as “unbreakable.”

Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection featur es of our

products. Attempts to break Microchip’ s code protection feature may be a violation of the Digit al Millennium Copyright Act. If such acts

allow unauthorized access to you r software or other copyrighted work, you may have a right to sue for relief under that Act.

Microchip received ISO/TS-16949:200 2 certif ication for its worldwide

headquarters, design and wafer fabrication facilities in Chandler and

Tempe, Arizona; Gresham, Oregon and design centers in California

and India. The Company’s quality system processes and procedures

are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hopping

devices, Serial EEPROMs, microperi pherals, nonvola tile memo ry and

analog product s. In addition, Microchip ’s quality system for the design

and manufacture of development systems is ISO 9001:2000 certified.

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10/05/07