TSI350 Datasheet, PDF (59/163 Pages) Integrated Device Technology – This chapter discusses the following

4. Transaction Ordering > General Ordering Guidelines
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The entries without superscripts reflect Tsi350’s implementation choices.
Table 9: Summary of Transaction Ordering
Can Row Pass Column?
Delayed Read Delayed Write Delayed Read
Bus Operation Posted Write
Request
Request
Completion
Posted Write
No¹
Delayed Read
No²
Request
Delayed Write
No⁴
Request
Delayed Read
No³
Completion
Yes⁵
No
No
Yes
Yes⁵
No
No
Yes
Yes⁵
Yes
Yes
No
Delayed Write
Yes
Yes
Yes
No
Completion
Delayed Write
Completion
Yes⁵
Yes
Yes
No
No
The following ordering rules describe the transaction relationships. Each ordering rule is followed by
an explanation. These ordering rules apply to posted write transactions, delayed write and read
requests, and delayed write and read completion transactions crossing Tsi350 in the same direction.
Note that delayed completion transactions cross Tsi350 in the direction opposite that of the
corresponding delayed requests.
1. Posted write transactions must complete on the target bus in the order in which they were received
on the initiator bus. The subsequent posted write transaction can be setting a flag that covers the
data in the first posted write transaction; if the second transaction were to complete before the first
transaction, a device checking the flag could subsequently consume stale data.
2. A delayed read request traveling in the same direction, as a previously queued posted write
transaction must push the posted write data ahead of it. The posted write transaction must complete
on the target bus before the delayed read request can be attempted on the target bus. The read
transaction can be to the same location as the write data, so if the read transaction were to pass the
write transaction, it would return stale data.
3. A delayed read completion must “pull” ahead of previously queued posted write data traveling in
the same direction. In this case, the read data is traveling in the same direction as the write data and
the initiator of the read transaction is on the same side of Tsi350 as the target of the write
transaction. The posted write transaction must complete to the target before the read data is
returned to the initiator. The read transaction can be to a status register of the initiator of the posted
write data and therefore should not complete until the write transaction is complete.
4. Delayed write requests cannot pass previously queued posted write data. As in the case of posted
memory write transactions, the delayed write transaction can be setting a flag that covers the data
in the posted write transaction; if the delayed write request were to complete before the earlier
posted write transaction, a device checking the flag could subsequently consume stale data.
Integrated Device Technology
www.idt.com
Tsi350 User Manual
January 10, 2014