MD87C51FB - Intel - Pdf.Support

November 1994 Order Number: 271093-007

M87C51FB

CHMOS SINGLE-CHIP 8-BIT MICROCONTROLLER WITH

16 KBYTES USER PROGRAMMABLE EPROM

Military

M87C51FB Ð 3.5 MHz to 12 MHz, VCC e5V

g20%

M87C51FB-16 Ð 3.5 MHz to 16 MHz, VCC e

5V g20%

YHigh Performance CHMOS EPROM

YThree 16-Bit Timer/Counters

YProgrammable Counter Array with:

Ð High Speed Output,

Ð Compare/Capture,

Ð Pulse Width Modulator,

Ð Watchdog Timer capabilities

YUp/Down Timer/Counter

YThree Level Program Lock System

Y16K On-Chip EPROM

Y256 Bytes of On-Chip Data RAM

YImproved Quick Pulse Programming

Algorithm

YBoolean Processor

YONCE (On-Circuit Emulation) Mode

YAvailable in 40-pin CERDIP and

44-pin Leadless Chip Carrier Packages

YGullwing and J-lead Packages Also

Available

Y32 Programmable I/O Lines

Y7 Interrupt Sources

YProgrammable Serial Channel with:

Ð Framing Error Detection

Ð Automatic Address Recognition

YTTL and CMOS Compatible Logic

Levels

Y64K External Program Memory Space

Y64K External Data Memory Space

YMCSÉ51 Microcontroller Fully

Compatible Instruction Set

YPower Saving Idle and Power Down

Modes

YMilitary Temperature Range:

b55§Ctoa

125§C(T

)

MEMORY ORGANIZATION

PROGRAM MEMORY: Up to 16 Kbytes of the program memory can reside in the on-chip EPROM. In addition

the device can address up to 64K of program memory external to the chip.

DATA MEMORY: This microcontroller has a 256 x 8 on-chip RAM. In addition it can address up to 64 Kbytes of

external data memory.

The Intel M87C51FB is a single-chip control-oriented microcontroller which is fabricated on Intel’s reliable

CHMOS III-E technology. Being a member of the MCS 51 family of microcontrollers, the M87C51FB uses the

same powerful instruction set, has the same architecture, and is pin-for-pin compatible with the existing

MCS 51 microcontroller family of products. The M87C51FB is an enhanced version of the M87C51. Its added

features make it an even more powerful microcontroller for applications that require Pulse Width Modulation,

High Speed I/O, and up/down counting capabilities such as motor control. It also has a more versatile serial

channel that facilitates multi-processor communications.

M87C51FB

271093–1

Figure 1. M87C51FB Block Diagram

M87C51FB

DIP

271093–2

LCC/GULLWING/J-LEAD

271093–20

Figure 2. M87C51FB Pin Connections

PIN DESCRIPTIONS

VCC: Supply voltage.

VSS: Circuit ground.

Port 0: Port 0 is an 8-bit, open drain, bidirectional I/O

port. As an output port each pin can sink several LS

TTL inputs. Port 0 pins that have 1’s written to them

float, and in that state can be used as high-imped-

ance inputs.

Port 0 is also the multiplexed low-order address and

data bus during accesses to external Program and

Data Memory. In this application it uses strong inter-

nal pullups when emitting1’s, and can source and

sink several LS TTL inputs.

Port 0 also receives the code bytes during EPROM

programming, and outputs the code bytes during

program verification. External pullup resistors are re-

quired during program verification.

Port 1: Port 1 is an 8-bit bidirectional I/O port with

internal pullups. The Port 1 output buffers can drive

LS TTL inputs. Port 1 pins that have 1’s written to

them are pulled high by the internal pullups, and in

that state can be used as inputs. As inputs, Port 1

pins that are externally being pulled low will source

current (IIL, on the data sheet) because of the inter-

nal pullups.

In addition, Port 1 serves the functions of the follow-

ing special features of the M87C51FB:

Port Pin Alternate Function

P1.0 T2 (External Count Input to Timer/

Counter 2)

P1.1 T2EX (Timer/Counter 2 Capture/

Reload Trigger and Direction Control)

P1.2 ECI (External Count Input to the PCA)

P1.3 CEX0 (External I/O for Compare/

Capture Module 0)

P1.4 CEX1 (External I/O for Compare/

Capture Module 1)

P1.5 CEX2 (External I/O for Compare/

Capture Module 2)

P1.6 CEX3 (External I/O for Compare/

Capture Module 3)

P1.7 CEX4 (External I/O for Compare/

Capture Module 4)

Port 1 receives the low-order address bytes during

EPROM programming and verifying.

Port 2: Port 2 is an 8-bit bidirectional I/O port with

internal pullups. The Port 2 output buffers can drive

LS TTL inputs. Port 2 pins that have 1’s written to

them are pulled high by the internal pullups, and in

that state can be used as inputs. As inputs, Port 2

pins that are externally being pulled low will source

current (IIL, on the data sheet) because of the inter-

nal pullups.

M87C51FB

Port 2 emits the high-order address byte during

fetches from external Program Memory and during

accesses to external Data Memory that use 16-bit

addresses (MOVX @DPTR). In this application it

uses strong internal pullups when emitting 1’s. Dur-

ing accesses to external Data Memory that use 8-bit

addresses (MOVX @Ri), Port 2 emits the contents of

the P2 Special Function Register.

Some Port 2 pins receive the high-order address bits

during EPROM programming and program verifica-

tion.

Port 3: Port 3 is an 8-bit bidirectional I/O port with

internal pullups. The Port 3 output buffers can drive

LS TTL inputs. Port 3 pins that have 1’s written to

them are pulled high by the internal pullups, and in

that state can be used as inputs. As inputs, Port 3

pins that are externally being pulled low will source

current (IIL, on the data sheet) because of the pull-

ups.

Port 3 also serves the functions of various special

features of the M8051 Family, as listed below:

Port Pin Alternate Function

P3.0 RXD (serial input port)

P3.1 TXD (serial output port)

P3.2 INT0 (external interrupt 0)

P3.3 INT1 (external interrupt 1)

P3.4 T0 (Timer 0 external input)

P3.5 T1 (Timer 1 external input)

P3.6 WR (external data memory write strobe)

P3.7 RD (external data memory read strobe)

RST: Reset input. A high on this pin for two machine

cycles while the oscillator is running resets the de-

vice. An internal pulldown resistor permits a power-

on reset with only a capacitor connected to VCC.

ALE: Address Latch Enable output pulse for latching

the low byte of the address during accesses to ex-

ternal memory. This pin (ALE/PROG) is also the

program pulse input during EPROM programming for

the M87C51FB.

In normal operation ALE is emitted at a constant

rate of (/6 the oscillator frequency, and may be used

for external timing or clocking purposes. Note, how-

ever, that one ALE pulse is skipped during each ac-

cess to external Data Memory.

Throughout the remainder of this data sheet, ALE

will refer to the signal coming out of the ALE/PROG

pin, and the pin will be referred to as the ALE/PROG

pin.

PSEN: Program Store Enable is the read strobe to

external Program Memory.

When the M87C51FB is executing code from exter-

nal Program Memory, PSEN is activated twice each

machine cycle, except that two PSEN activations

are skipped during each access to external Data

Memory.

EA/VPP: External Access enable. EA must be

strapped to VSS in order to enable the device to

fetch code from external Program Memory locations

0000H to 0FFFFH. Note, however, that if either of

the Program Lock bits are programmed, EA will be

internally latched on reset.

EA should be strapped to VCC for internal program

executions.

This pin also receives the programming supply volt-

age (VPP) during EPROM programming.

XTAL1: Input to the inverting oscillator amplifier.

XTAL2: Output from the inverting oscillator amplifier.

OSCILLATOR CHARACTERISTICS

XTAL1 and XTAL2 are the input and output, respec-

tively, of an inverting amplifier which can be config-

ured for use as an on-chip oscillator, as shown in

Figure 3. Either a quartz crystal or ceramic resonator

may be used. More detailed information concerning

the use of the on-chip oscillator is available in Appli-

cation Note AP-155, ‘‘Oscillators for Microcontrol-

lers.’’

To drive the device from an external clock source,

XTAL1 should be driven, while XTAL2 floats, as

shown in Figure 4. There are no requirements on the

duty cycle of the external clock signal, since the in-

put to the internal clocking circuitry is through a di-

vide-by-two flip-flop, but minimum and maximum

high and low times specified on the data sheet must

be observed.

271093–3

C1, C2 e30 pF g10 pF for Crystals

e10 pF for Ceramic Resonators

Figure 3. Oscillator Connections

M87C51FB

271093–4

Figure 4. External Clock Drive Configuration

IDLE MODE

The user’s software can invoke the Idle Mode. When

the microcontroller is in this mode, power consump-

tion is reduced. The Special Function Registers and

the onboard RAM retain their values during Idle, but

the processor stops executing instructions. Idle

Mode will be exited if the chip is reset or if an en-

abled interrupt occurs. The PCA timer/counter can

optionally be left running or paused during Idle

Mode.

POWER DOWN MODE

To save even more power, a Power Down Mode can

be invoked by software. In this mode, the oscillator

is stopped and the instruction that invoked Power

Down is the last instruction executed. The on-chip

RAM and Special Function Registers retain their val-

ues until the Power Down Mode is terminated.

On the M87C51FB either a hardware reset or an

external interrupt can cause an exit from Power

Down. Reset redefines all the SFRs but does not

change the on-chip RAM. An external interrupt al-

lows both the SFRs and on-chip RAM to retain their

values.

To properly terminate Power Down the reset or ex-

ternal interrupt should not be executed before VCC is

restored to its normal operating level and must be

held active long enough for the oscillator to restart

and stabilize (normally less than 10 ms).

With an external interrupt, INT0 and INT1 must be

enabled and configured as level-sensitive. Holding

the pin low restarts the oscillator but bringing the pin

back high completes the exit. Once the interrupt is

serviced, the next instruction to be executed after

RETI will be the one following the instruction that

puts the device into Power Down.

DESIGN CONSIDERATION

#Ambient light is known to affect the internal RAM

contents during operation. If the M87C51FB ap-

plication requires the part to be run under ambi-

ent lighting, an opaque label should be placed

over the window to exclude light.

#When the Idle Mode is terminated by a hardware

reset, the device normally resumes program exe-

cution, from where it left off, up to two machine

cycles before the internal reset algorithm takes

control. On-chip hardware inhibits access to inter-

nal RAM in this event, but access to the port pins

is not inhibited. To eliminate the possibility of an

unexpected write when Idle is terminated by re-

set, the instruction following the one that invokes

Idle should not be one that writes to a port pin or

to external memory.

ONCE MODE

The ONCE (‘‘On-Circuit Emulation’’) Mode facilitates

testing and debugging of systems using the

M87C51FB without the M87C51FB having to be re-

moved from the circuit. The ONCE Mode is invoked

by:

1) Pull ALE low while the device is in reset and

PSEN is high;

2) Hold ALE low as RST is deactivated.

While the device is in ONCE Mode, the Port 0 pins

go into a float state, and the other port pins and ALE

and PSEN are weakly pulled high. The oscillator cir-

cuit remains active. While the M87C51FB is in this

mode, an emulator or test CPU can be used to drive

the circuit. Normal operation is restored when a nor-

mal reset is applied.

Table 1. Status of the External Pins during Idle and Power Down

Mode Program ALE PSEN PORT0 PORT1 PORT2 PORT3

Memory

Idle Internal 1 1 Data Data Data Data

Idle External 1 1 Float Data Address Data

Power Down Internal 0 0 Data Data Data Data

Power Down External 0 0 Float Data Data Data

NOTE:

For more detailed information on the reduced power modes refer to Application Note AP-255, ‘‘Designing with the

M80C51BH’’.

M87C51FB

ABSOLUTE MAXIMUM RATINGS*

Case Temperature Under Bias

ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀb55§Ctoa

125§C

Storage Temperature ÀÀÀÀÀÀÀÀÀÀb65§Ctoa

150§C

Voltage on EA/VPP Pin to VSS ÀÀÀÀÀÀÀ0V to a13.0V

Voltage on Any Other Pin to VSS ÀÀb0.5V to a6.5V

Maximum IOL Per I/O Pin ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ15 mA

Power DissipationÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ1.5W

(based on PACKAGE heat transfer limitations, not

device power consumption)

NOTICE: This is a production data sheet. The specifi-

cations are subject to change without notice.

WARNING: Stressing the device beyond the ‘‘Absolute

Maximum Ratings’’ may cause permanent damage.

These are stress ratings only. Operation beyond the

‘‘Operating Conditions’’ is not recommended and ex-

tended exposure beyond the ‘‘Operating Conditions’’

may affect device reliability.

Operating Conditions

Symbol Description Min Max Unit

TCCase Temperature (Instant On) b55 a125 §C

VCC Digital Supply Voltage 4.0 6.0 V

fOSC Oscillator Frequency 3.5 16 MHz

DC CHARACTERISTICS: (Over Specified Operating Conditions)

Symbol Parameter Min Max Unit Test Conditions

VIL Input Low Voltage b0.5 0.2 VCCb0.1 V

VIH Input High Voltage 0.2 VCCa0.9 VCCa0.5 V

(Except XTAL1, RST)

VIH1 Input High Voltage (XTAL1, RST) 0.7 VCC VCCa0.5 V

VOL Output Low Voltage(5) 0.3 V IOL e100 mA (Note 1)

(Ports 1, 2, and 3) 0.45 V IOL e1.6 mA (Note 1)

1.0 V IOL e3.5 mA (Notes 1, 4)

VOL1 Output Low Voltage(5) 0.3 V IOL e200 mA (Note 1)

(Port 0, ALE, PSEN) 0.45 V IOL e3.2 mA (Note 1)

1.0 V IOL e7.0 mA (Note 1, 4)

VOH Output High Voltage VCCb0.3 V IOH eb

10 mA

(Ports 1, 2, and 3) VCCb0.7 V IOH eb

30 mA

VCCb1.5 V IOH eb

60 mA

M87C51FB

DC CHARACTERISTICS: (Over Specified Operating Conditions) (Continued)

Symbol Parameter Min Max Unit Test Conditions

VOH1 Output High Voltage VCCb0.3 V IOH eb

200 mA (Note 2)

(Port 0 in External Bus Mode, VCCb0.7 V IOH eb

3.2 mA

ALE, PSEN)

VCCb1.5 V IOH eb

7.0 mA (Note 4)

IIL Logical 0 Input Current b75 mAV

IN e0.45V

(Ports 1, 2, and 3)

ILI Input leakage Current (Port 0) g10 mA 0.45V kVIN kVCC

ITL Logical 1 to 0 Transition Current b750 mAV

IN e2V

(Ports 1, 2, and 3)

RRST RST Pulldown Resistor 40 225 KX

CIO Pin Capacitance 10 pF @1 MHz, 25§C

ICC Power Supply Current: (Note 3)

Active Mode @16 MHz 45 mA

Idle Mode @16 MHz 15 mA

Power Down Mode @16 MHz 130 mA

NOTES:

1. Capacitive loading on Ports 0 and 2 may cause spurious noise pulses to be superimposed on the VOLs of ALE and Ports

1 and 3. The noise is due to external bus capacitance discharging into the Port 0 and Port 2 pins when these pins make 1 to

0 transitions during bus operations. In applications where capacitance loading exceeds 100 pFs, the noise pulse on the ALE

signal may exceed 0.8V. In these cases, it may be desirable to qualify ALE with a Schmitt Trigger, or use an Address Latch

with a Schmitt Trigger Strobe input.

2. Capacitive loading on Ports 0 and 2 cause the VOH on ALE and PSEN to drop below the VCC b0.3 specification when

the address lines are stabilizing.

3. See Figures 5–8 for load circuits. Minimum VCC for Power Down is 2V.

4. Care must be taken not to exceed the maximum allowable power dissipation.

5. Under steady state (non-transient) conditions, IOL must be externally limited as follows:

Maximum IOL per port pin: 10mA

Maximum IOL per 8-bit portÐ

Port 0: 26 mA

Ports 1, 2 and 3: 15 mA

Maximum total IOL for all output pins: 71 mA

If IOL exceeds the test condition, VOL may exceed the related specification. Pins are not guaranteed to sink current greater

than the listed test conditions.

271093–5

All other pins disconnected

TCLCH eTCHCL e5ns

Figure 5. ICC Load Circuit Active Mode

271093–6

All other pins disconnected

TCLCH eTCHCL e5ns

Figure 6. ICC Load Circuit Idle Mode

M87C51FB

271093–7

All other pins disconnected

Figure 7. ICC Load Circuit Power Down Mode.

VCC e2.0V to 5.5V.

271093–8

Figure 8. Clock Signal Waveform for ICC Tests in Active and Idle Modes. TCLCH eTCHCL e5 ns.

EXPLANATION OF THE AC SYMBOLS

Each timing symbol has 5 characters. The first char-

acter is always a ‘T’ (stands for time). The other

characters, depending on their positions, stand for

the name of a signal or the logical status of that

signal. The following is a list of all the characters and

what they stand for.

A: Address

C: Clock

D: Input Data

H: Logic level HIGH

I: Instruction (program memory contents)

L: Logic level LOW, or ALE

P: PSEN

Q: Output Data

R: RD signal

T: Time

V: Valid

W: WR signal

X: No longer a valid logic level

Z: Float

For example,

TAVLL eTime from Address Valid to ALE Low

TLLPL eTime from ALE Low to PSEN Low

M87C51FB

AC CHARACTERISTICS (Over Specified Operating Conditions)

EXTERNAL PROGRAM MEMORY CHARACTERISTICS

12 MHz 16 MHz Variable

Symbol Parameter Oscillator Oscillator Oscillator Unit

Min Max Min Max Min Max

1/TCLCL Oscillator Frequency

87C51FB 3.5 12 MHz

87C51FB-16 3.5 16

TLHLL ALE Pulse Width 127 85 2TCLCLb40 ns

TAVLL Address Valid to ALE Low 43 23 TCLCLb40 ns

TLLAX Address Hold After ALE Low 53 33 TCLCLb30 ns

TLLIV ALE Low to 234 150 4TCLCLb100 ns

Valid Instruction In

TLLPL ALE Low to PSEN Low 53 33 TCLCLb30 ns

TPLPH PSEN Pulse Width 205 143 3TCLCLb45 ns

TPLIV PSEN Low to 145 83 3TCLCLb105 ns

Valid Instruction In

TPXIX Input Instruction Hold 0 0 0 ns

After PSEN

TPXIZ Input Instruction Float 59 38 TCLCLb25 ns

After PSEN

TAVIV Address to 312 208 5TCLCLb105 ns

Valid Instruction In

TPLAZ PSEN Low to Address Float 10 10 10 ns

TRLRH RD Pulse Width 400 275 6TCLCLb100 ns

TWLWH WR Pulse Width 400 275 6TCLCLb100 ns

TRLDV RD Low to Valid Data In 252 147.5 5TCLCLb165 ns

TRHDX Data Hold After RD 00 0 ns

TRHDZ Data Float After RD 107 65 2TCLCLb60 ns

TLLDV ALE Low to Valid Data In 517 350 8TCLCLb150 ns

TAVDV Address to Valid Data In 585 398 9TCLCLb165 ns

TLLWL ALE Low to RD or WR Low 200 300 138 238 3TCLCLb50 3TCLCLa50 ns

TAVWL Address Valid to WR Low 203 120 4TCLCLb130 ns

TQVWX Data Valid before WR 33 13 TCLCLb50 ns

TWHQX Data Hold after WR 33 13 TCLCLb50 ns

TQVWH Data Valid to WR High 433 288 7TCLCLb150 ns

TRLAZ RD Low to Address Float 0 0 0 ns

TWHLH RD or WR High to ALE High 43 123 23 103 TCLCLb40 TCLCLa40 ns

NOTE:

7. Case temperatures are ‘‘instant on’’.

M87C51FB

EXTERNAL PROGRAM MEMORY READ CYCLE

271093–9

EXTERNAL DATA MEMORY READ CYCLE

271093–10

EXTERNAL DATA MEMORY WRITE CYCLE

271093–11

M87C51FB

SERIAL PORT TIMING - SHIFT REGISTER MODE

Test Conditions: (Over Specified Operating Conditions)

12 MHz 16 MHz Variable

Symbol Parameter Oscillator Oscillator Oscillator Units

Min Max Min Max Min Max

TXLXL Serial Port Clock Cycle Time 1 0.75 12TCLCL ms

TQVXH Output Data Setup to Clock 700 492 10TCLCLb133 ns

Rising Edge

TXHQX Output Data Hold after 50 8 2TCLCLb117 ns

Clock Rising Edge

TXHDX Input Data Hold After Clock 0 0 0 ns

Rising Edge

TXHDV Clock Rising Edge to Input 700 492 10TCLCLb133 ns

Data Valid

SHIFT REGISTER MODE TIMING WAVEFORMS

271093–12

EXTERNAL CLOCK DRIVE

Symbol Parameter Min Max Units

1/TCLCL Oscillator Frequency

87C51FB 3.5 12 MHz

87C51FB-16 3.5 16

TCHCX High Time 20 ns

TCLCX Low Time 20 ns

TCLCH Rise Time 20 ns

TCHCL Fall Time 20 ns

EXTERNAL CLOCK DRIVE WAVEFORM

271093–13

M87C51FB

AC TESTING INPUT, OUTPUT WAVEFORMS

271093–14

AC Inputs during testing are driven at VCCb0.5V for a Logic ‘‘1’’

and 0.45V for a Logic ‘‘0’’. Timing measurements are made at VIH

min for a Logic ‘‘1’’ and VIL max for a Logic ‘‘0’’.

FLOAT WAVEFORMS

271093–15

For timing purposes a port pin is no longer floating when a

100 mV change from load voltage occurs, and begins to float

when a 100 mV change from the loaded VOH/VOL level occurs.

IOL/IOH tg20 mA.

EPROM CHARACTERISTICS

Table 2 shows the logic levels for programming the

Program Memory, the Encryption Table, and the

Lock Bits and for reading the signature bytes.

Table 2. EPROM Programming Modes

Mode RST PSEN ALE/ EA/ P2.6 P2.7 P3.3 P3.6 P3.7

PROG VPP

Program Code Data H L ß12.75V L H H H H

Verify Code Data H L H H L L L H H

Program Encryption H L ß12.75V L H H L H

Array Address 0– 3FH

Program Lock Bit 1 H L ß12.75V H H H H H

Bits Bit 2 H L ß12.75V H H H L L

Bit 3 H L ß12.75V H L H H L

Read Signature Byte H L H H L L L L L

NOTES:

‘‘1’’ eValid high for that pin

‘‘0’’ eValid low for that pin

‘‘VPP’’ ea

12.75V g0.25V

DEFINITION OF TERMS

ADDRESS LINES: P1.0– P1.7, P2.0– P2.5, P3.4–

P3.5 respectively for A0– A15.

DATA LINES: P0.0– P0.7 for D0– D7.

CONTROL SIGNALS: RST, PSEN, P2.6, P2.7, P3.3,

P3.6, P3.7.

PROGRAM SIGNALS: ALE/PROG,EA/VPP.

PROGRAMMING THE EPROM

The part must be running with a 4 MHz to 6 MHz

oscillator. The address of an EPROM location to be

programmed is applied to address lines while the

code byte to be programmed in that location is ap-

plied to data lines. Control and program signals must

be held at the levels indicated in Table 2. Normally

EA/VPP is held at logic high until just before ALE/

PROG is to be pulsed. The EA/VPP is raised to VPP,

ALE/PROG is pulsed low and then EA/VPP is re-

turned to a high (also refer to timing diagrams).

NOTE:

Exceeding the VPP maximum for any amount of

time could damage the device permanently. The

VPP source must be well regulated and free of

glitches.

M87C51FB

271093–16

*See Table 2 for proper input on these pins.

Figure 9. Programming the EPROM

PROGRAMMING ALGORITHM

Refer to Table 2 and Figures 9 and 10 for address,

data, and control signals set up. To program the

M87C51FB the following sequence must be exer-

cised.

1. Input the valid address on the address lines.

2. Input the appropriate data byte on the data

lines.

3. Activate the correct combination of control sig-

nals.

4. Raise EA/VPP from VCC to 12.75V g0.25V.

5. Pulse ALE/PROG 5 times for the EPROM ar-

ray, and 25 times for the encryption table and

the lock bits.

Repeat 1 through 5 changing the address and data

for the entire array or until the end of the object file is

reached.

PROGRAM VERIFY

Program verify may be done after each byte that is

programmed, or after a block of bytes that is pro-

grammed. In either case a complete verify of the

entire array that has been programmed will ensure a

reliable programming of the M87C51FB.

The lock bits cannot be directly verified. Verification

of the lock bits is done by observing that their fea-

tures are enabled. Refer to the EPROM Program

Lock section in this data sheet.

271093–17

5 Pulses

Figure 10. Programming Signal’s Waveforms

M87C51FB

EPROM Program Lock

The two-level Program Lock system consists of two

Program Lock bits and a 32 byte Encryption Array

which are used to protect the program memory

against software piracy.

Encryption Array

Within the EPROM array are 32 bytes of Encryption

Array that are initially unprogrammed (all 1’s). Every

time that a byte is addressed during a verify, 5 ad-

dress lines are used to select a byte of the Encryp-

tion Array. This byte is then exclusive-NOR’ed

(XNOR) with the code byte, creating an Encrypted

Verify byte. The algorithm, with the array in the un-

programmed state (all 1’s), will return the code in it’s

original, unmodified form.

Program Lock Bits

Also included in the EPROM Program Lock scheme

are two Program Lock Bits which are programmed

as shown in Table 2.

Table 3 outlines the features of programming the

Lock Bits.

Erasing the EPROM also erases the Encryption Ar-

ray and the Program Lock Bits, returning the part to

full functionality.

Reading the Signature Bytes

The signature bytes are read by the same procedure

as a normal verification of locations 030H, 031H and

60H. To read these bytes, follow the procedure for

EPROM verify, but activate the control lines provid-

ed in Table 2 for Read Signature Byte.

Location: 30H e89H

31H e58H

60H eFBH

Erasure Characteristics

Erasure of the EPROM begins to occur when the

chip is exposed to light with wavelength shorter than

approximately 4,000 Angstroms. Since sunlight and

fluorescent lighting have wavelengths in this range,

exposure to these light sources over an extended

time (about 1 week in sunlight, or 3 years in room-

level fluorescent lighting) could cause inadvertent

erasure. If an application subjects the device to this

type of exposure, it is suggested that an opaque la-

bel be placed over the window.

The recommended erasure procedure is exposure

to ultraviolet light (at 2537 Angstroms) to an integrat-

ed dose of at least 15 W-sec/cm2. Exposing the

EPROM to an ultraviolet lamp of 12,000 mW/cm2

rating for 30 minutes, at a distance of about 1 inch,

should be sufficient.

Erasure leaves all the EPROM Cells in a 1’s state.

Table 3. Program Lock Bits and their Features

Program Lock Bits Logic Enabled

LB1 LB2

U U No Program Lock features enabled. (Code Verify will still be

encrypted by the Encryption Array.)

P U MOVC instructions executed from external program memory

are disabled from fetching code bytes from internal memory,

EA is sampled and latched on reset, and further programming

of the EPROM is disabled.

P P Same as above, but Verify is also disabled

U P Reserved for Future Definition

M87C51FB

EPROM PROGRAMMING AND VERIFICATION CHARACTERISTICS

(TAe21§Cto27

C; VCC e5Vg0.25V; VSS e0V)

ADVANCED INFORMATIONÐCONTACT INTEL FOR DESIGN-IN INFORMATION

Symbol Parameter Min Max Units

VPP Programming Supply Voltage 12.5 13.0 V

IPP Programming Supply Current 50 mA

1/TCLCL Oscillator Frequency 4 6 MHz

TAVGL Address Setup to PROG Low 48TCLCL

TGHAX Address Hold after PROG 48TCLCL

TDVGL Data Setup to PROG Low 48TCLCL

TGHDX Data Hold after PROG 48TCLCL

TEHSH P2.7 (ENABLE) High to VPP 48TCLCL

TSHGL VPP Setup to PROG Low 10 ms

TGHSL VPP Hold after PROG 10 ms

TGLGH PROG Width 90 110 ms

TAVQV Address to Data Valid 48TCLCL

TELQV ENABLE Low to Data Valid 48TCLCL

TEHQZ Data Float after ENABLE 0 48TCLCL

TGHGL PROG High to PROG Low 10 ms

EPROM PROGRAMMING AND VERIFICATION WAVEFORMS

271093–19