Intel
®
81341 and 81342—Address Translation Unit (PCI Express)
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
258
Order Number: 315037-002US
3.3.5.3
Outbound PCI Express* Message Transactions
The ATU provides a port programming model to generate outbound PCI Express
messages.
Generating an outbound message transaction to the PCI Express interface involves up
to 5 internal bus cycles.
1. Write outbound message transaction header registers 0 - 3.
2. Write the data to the outbound message transaction payload register. This write
causes the generation of the message TLP on the PCI Express interface.
Note:
When the payload length is 0, a write to the payload register is still required but the
written data is ignored and not sent as part of the message TLP.
3.3.5.4
Completion Timeout Mechanism
The ATU implements a completion timeout mechanism on all outbound requests that
require completions. The timeout mechanism is fixed and ensures an expiration time
between 16 and 32 ms.