82375EB datasheet(18/131 Pages) INTEL

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82375EBSB

22 PCI Arbiter Signals

Pin Name

Type

Description

CPUREQ

CPU REQUEST

CPUREQ

asserted indicates that the Host CPU requests use of

the PCI Bus During PCIRST

this signal must be sampled high by the PCEB When

PCIRST

is asserted (and CPUREQ

is sampled high) the PCEB drives the AD

CBE

and PAR signals to keep them from floating

REQ 30

REQUEST

A bus master asserts the corresponding request signal to request the

PCI Bus

CPUGNT

out

CPU GRANT

The PCEB asserts CPUGNT

to indicate that the CPU master (Host

Bridge) has been granted the PCI Bus During PCI reset CPUGNT

is tri-stated

GNT 30

out

GRANT

The PCEB asserts one of the GNT 30 signals to indicate that the

corresponding PCI master has been granted the PCI Bus During PCI reset these

signals are tri-stated

MEMREQ

out

MEMORY REQUEST

If the PCEB is configured in Guaranteed Access Time (GAT)

Mode MEMREQ

is asserted when an EISA device or DMA requests the EISA Bus

The PCEB asserts this signal (along with FLSHREQ ) to indicate that the PCEB

requires ownership of main memory The PCEB asserts FLSHREQ

concurrently

with asserting MEMREQ

This signal is synchronous to the PCI clock During reset

this signal is driven high

FLSHREQ

MEMREQ

Meaning

Idle

Flush buffers pointing towards PCI

to avoid ISA deadlock

GAT enabled or disabled For buffer

coherency in APIC systems the

buffers pointing to main memory

must be flushed and disabled for the

duration of assertion

GAT mode Guarantee PCI Bus

immediate access to main memory

(this may or may not require the

PCI-to-main memory buffers to be

flushed first depending on the

number of buffers)

FLSHREQ

out

FLUSH REQUEST

FLSHREQ

is asserted by the PCEB to command all of the

system’s posted write buffers pointing towards PCI to be flushed This is required

before granting the EISA Bus to an EISA master or the DMA Note that for APIC

related buffer flush requests this signal is negated This signal is synchronous to the

PCI clock During reset this signal is driven high

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