82545GM — Networking Silicon
10 Datasheet
3.2.1 PCI Address, Data and Control Signals
Symbol Type Name and Function
AD[63:0] TS
Address and Data. Address and data signals are multiplexed on the same PCI pins. A
bus transaction includes an address phase followed by one or more data phases.
The address phase is the clock cycle when the Frame signal (FRAME#) is asserted
low. During the address phase AD[63:0] contain a physical address (64 bits). For I/O,
this is a byte address, and for configuration and memory, a DWORD address. The
82545GM device uses little endian byte ordering.
During data phases, AD[7:0] contain the least significant byte (LSB) and AD[63:56]
contain the most significant byte (MSB).
The 82545GM controller may optionally be connected to a 32-bit PCI bus. On the 32-bit
bus, AD[63:32] and other signals corresponding to the high order byte lanes do not
participate in the bus cycle.
CBE[7:0]# TS
Bus Command and Byte Enables. Bus command and byte enable signals are
multiplexed on the same PCI pins. During the addr ess phase of a transaction,
CBE[7:0]# define the bus command. In the data phase, CBE[7:0]# are used as byte
enables. The byte enables are valid for the entire data phase and determine which byte
lanes contain meaningful data.
CBE0# applies to byte 0 (LSB) and CBE7# applies to byte 7 (MSB).
PAR TS
Parity. The Parity signal is issued to implement even parity across AD[31:0] and
CBE[3:0]#. PAR is stable and valid one clock after the address phase. During data
phases, PAR is stable and valid one clock after either IRDY# is asserted on a write
transaction or TRDY# is asserted after a read transaction. Once P AR is valid, it remains
valid until one clock after the completion of the current data phase.
When the 82545GM controller is a bus master, it drives PAR for address and write data
phases, and as a slave device, drives PAR for read data phases.
PAR64 TS
Parity 64. The Parity 64 signal is issued to implement even parity across AD[63:32]
and CBE[7:4]#. PAR64 is stable and valid one clock after the address phase. During
data phases, PAR64 is stable and valid one clock after either IRDY# is asserted on a
write transaction or TRDY# is asserted after a read transaction. Once PAR64 is valid, it
remains valid until one clock after the completion of the current data phase.
When the 82545GM controller is a bus master, it drives PAR64 for address and write
data phases, and as a slave device, drives PAR64 for read data phases.
FRAME# STS Cycle Frame. The Frame signal is driven by the 82545GM device to indicate the
beginning and length of an access and indicate the beginning of a bus transaction.
While FRAME# is asserted, data transfers continue. FRAME# is de-asserted when the
transaction is in the final data phase.
IRDY# STS
Initiator Ready. Initiator Ready indicates the ability of the 82545GM controller (as bus
master device) to complete the current data phase of the transaction. IRDY# is used in
conjunction with the Target Ready signal (TRDY#). The data phase is completed on
any clock when both IRDY# and TRDY# are asserted.
During the write cycle, IRDY# indicates that valid data is present on AD[63:0]. For a
read cycle, it indicates the master is ready to accept data. Wait cycles are inserted until
both IRDY# and TRDY# are asserted togeth e r. The 82545GM controller drives IRDY#
when acting as a master and samples it when acting as a slave.
TRDY# STS
Target Ready. The Target Ready signal indicates the ability of the 82545GM controller
(as a selected device) to complete the current data phase of the transaction. TRDY# is
used in conjunction with the Initiator Ready signal (IRDY#). A data phase is comp leted
on any clock when both TRDY# and IRDY# are sampled asserted.
During a read cycle, TRDY# indicates that valid data is present on AD[63:0]. For a write
cycle, it indicates the target is ready to accept data. Wait cycles are inserted until both
IRDY# and TRDY# are asserted together. The 82545GM device drives TRDY# when
acting as a slave and samples it when acting as a master.