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Message
From: arora.pra at gmail.com<arora.pra@g...>
Date: Tue Apr 24 04:11:30 CEST 2007
Subject: [pci] flushing of un-read data
Hi,The PCI IP Core Spec (Rev 1.2) mentions that 'any data not read
from the PCIR_FIFO is flushed immediately after the read
transaction is finished...' (pg. 34).
We have a data FIFO that will be read as a target over PCI. Each
read leads to a pop of the data FIFO. If the PCIR_FIFO has
prefetched data from the data fifo and get flushed, this data is lost.
The FIFO state changes on each pop so there's no way to recover
the lost data.
A couple of questions:
1) Is there a mode where the prefetched data is not flushed on
completion of the PCI transaction? Some commercial cores seem to
support such a mode for FIFO-like applications.
2) Does the core indicate how many prefetched words were
flushed? Given this information, it might be possible to implement a
rollback mechanism externally.
Thanks,
Prashant Arora
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