pi7c8150b Pericom Semiconductor Corporation, pi7c8150b Datasheet - Page 46

• Manufacturer Part Number: pi7c8150b
• Description: Asynchronous 2-port Pci Bridge
• Manufacturer: Pericom Semiconductor Corporation

06-0044
5
5.1
Note: If both the VGA mode bit and the VGA snoop bit are set, PI7C8150B behaves in the
same way as if only the VGA mode bit were set.
TRANSACTION ORDERING
To maintain data coherency and consistency, PI7C8150B complies with the ordering rules
set forth in the PCI Local Bus Specification, Revision 2.3, for transactions crossing the
bridge. This chapter describes the ordering rules that control transaction forwarding across
PI7C8150B.
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.
Page 46 of 108
ASYNCHRONOUS 2-PORT PCI-TO-PCI BRIDGE
APRIL 2006 – Revision 2.02
PI7C8150B