PI7C8150BMA-33 datasheet(47/107 Pages) PERICOM

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PI7C8150B

ASYNCHRONOUS 2-PORT PCI-TO-PCI BRIDGE

Page 47 of 107

April 2015 – Revision 2.1

5.1

TRANSACTIONS GOVERNED BY ORDERING RULES

Ordering relationships are established for the following classes of transactions crossing

PI7C8150B:

Posted write transactions, comprised of memory write and memory write and

invalidate transactions.

Posted write transactions complete at the source before they complete at the destination;

that is, data is written into intermediate data buffers before it reaches the target.

Delayed write request transactions, comprised of I/O write and configuration write

transactions.

Delayed write requests are terminated by target retry on the initiator bus and

are queued in the delayed transaction queue. A delayed write transaction must complete on

the target bus before it completes on the initiator bus.

Delayed write completion transactions, comprised of I/O write and configuration

write transactions.

Delayed write completion transactions complete on the target bus, and the target response

is queued in the buffers. A delayed write completion transaction proceeds

in the direction opposite that of the original delayed write request; that is, a delayed write

completion transaction proceeds from the target bus to the initiator bus.

Delayed read request transactions, comprised of all memory read, I/O read, and

configuration read transactions.

Delayed read requests are terminated by target retry on the initiator bus and are queued in

the delayed transaction queue.

Delayed read completion transactions, comprised of all memory read, I/O read, &

configuration read transactions.

Delayed read completion transactions complete on the target bus, and the read data is

queued in the read data buffers. A delayed read completion transaction proceeds in the

direction opposite that of the original delayed read request; that is, a delayed read

completion transaction proceeds from the target bus to the initiator bus.

PI7C8150B does not combine or merge write transactions:



PI7C8150B does not combine separate write transactions into a single write

transaction—this optimization is best implemented in the originating master.



PI7C8150B does not merge bytes on separate masked write transactions to the same

DWORD address—this optimization is also best implemented in the originating

master.



PI7C8150B does not collapse sequential write transactions to the same address into a

single write transaction—the PCI Local Bus Specification does not permit this

combining of transactions.

5.2

GENERAL ORDERING GUIDELINES

Independent transactions on primary and secondary buses have a relationship only when

those transactions cross PI7C8150B.

The following general ordering guidelines govern transactions crossing PI7C8150B:

15-0048

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