82375EB datasheet(75/131 Pages) INTEL

75 / 131 page

82375EBSB

290477 – 54

Figure 12 PCI Interrupt Acknowledge Cycle

518 EXCLUSIVE ACCESS

Refer to Figure 13 Figure 14 and Figure 15 for exclusive access timing relationships

Target support

PCI provides an exclusive access mechanism that allows non-exclusive accesses to proceed in the face of

exclusive accesses This is referred to as a Resource Lock (Note that the exclusive access mechanism that

locks the entire bus is Bus Lock) The PCEB as a resource can be locked by any PCI initiator In the context

of locked cycles the PCEB and entire EISA subsystem are considered a single resource (EISA subsystem is

indirectly locked during an exclusive access to the PCEB) A locked access to any address contained within

the EISA subsystem locks the entire subsystem from the PCI side The PLOCK

signal is propagated to the

EISA LOCK

signal Note that write posting (PCI-to-EISA) is disabled for PCI locked cycles propagated to the

EISA subsystem The EISA Bus is not released to ESC until the locked sequence is complete A subsequent

PCI initiator access to the EISA subsystem while it is locked results in a retry The PCEB becomes locked

when it is the target of the access and PLOCK

is sampled negated during the address phase The PCEB

remains locked until FRAME

and PLOCK

are both sampled negated When in a locked state the PCEB

only accepts requests when PLOCK

is sampled negated during the address phase If PLOCK

is asserted

during the address phase the PCEB responds by asserting STOP

with TRDY

negated (RETRY)

As an unlocked target the PCEB ignores PLOCK

when deciding if it should respond to a PCI address

decoder hit Also if PLOCK

is sampled asserted during an address phase the PCEB does not go into a

locked state

As a locked target the PCEB responds to an initiator when it samples PLOCK

negated during the address

phase of the cycle in which the PCEB is the target of the access The locking master may negate PLOCK

the end of the last data phase When FRAME

and PLOCK

are both sampled negated the PCEB goes to

the unlocked state

Note that the PCEB does not release the EISA Bus when it is in the locked state

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