82540EP — Networking Silicon
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C/BE#[3:0] TS
Bus Command and Byte Enables. Bus command and byte enable signals are
multiplexed on the same PCI pins. During the address phase of a transaction, C/
BE#[3:0] define the bus command. In the data phase, C/BE#[3:0] are used as byte
enables. The byte enables are valid for the ent ire dat a phase and determine which byte
lanes contain meaningful data.
C/BE#[0] applies to byte 0 (LSB) and C/BE#[3] applies to byte 3 (MSB).
PAR TS
Parity. T he Parity signal is issued to implement even parity across AD[31:0] and C/
BE#[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 aft er a read transaction. Once P AR is valid, it remains
valid until one clock after the completion of the current data phase.
When the 82540EP 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.
FRAME# STS C ycle Frame. The Fra me sig na l i s dr iven by the 82540EP 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 82540E P 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[31:0]. For a
read cycle, it indicates the master is ready to accept data. W ait cycles are inserted until
both IRDY# and TRDY# are asserted together. The 82540EP 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 82540EP controller
(as a selected device) to complete the current dat a phase of the transaction. TRDY# is
used in conjunction with the Initiator Ready signal (IRDY#). A data phase is completed
on any clock when both TRDY# and IRDY# are sampled asserted.
During a read cycle, TRDY# indicates that valid data is present on AD[31:0]. 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 82540EP device drives TRDY# when
acting as a slave and samples it when acting as a master.
STOP# STS
Stop. The Stop signal indicates the current target is requesting the master to stop the
current transaction. As a slave, the 82540EP controller drives STOP# to request the
bus master to stop the transaction. As a master, the 82540EP controller receives
STOP# from the slave to stop the current transaction.
IDSEL# I Initia lization Device Select. The Initialization Device Select signal is used by the
82540EP as a chip select signal during configuration read and write transactions.
DEVSEL# STS
Device Select. When the Device Select signal is actively driven by the 82540EP, it
signals notifies the bus master that it has decoded its addres s as the target of the
current access. As an input, DEVSEL# indicates whether any device on the bus has
been selected.
VIO P
VIO. The VI O signal is a voltage reference for the PCI interface (3.3 V or 5 V PCI
signaling environment). It is used as the clamping voltage.
Note: An external resistor is required between the voltage reference and the VIO pin.
The target resistor value is 100 K Ω
Symbol Type Name and Function