Host Bridge: Read Retry

[Pavel.Peleska@mch.scn.de]

Hallo experts,

we intend to use the synthesizable PCI core for our host bridge design, 
with four entry deep address fifos in the target path. We are wondering 
what happens in the following scenario:

Two (or more) PCI devices are permanently writing to the host bridge, e.g. 
with single writes, so that the address fifo is always filled with one or 
more addresses which supposingly leads to any PCI device initiating a read 
from the host bridge to experience a retry. Is this correct?

Is it a correct behaviour of a host bridge to return a retry to a PCI 
device if the address fifo is not empty, i.e. a queued write has to be 
processed first? Does this lead to a situation where the read from the core 
will not come through? Or should the host bridge not accept any write 
operation until the retryed read operation will be serviced and completed?

Is using a one level deep address fifo a remedy?

Thanx in advance for any comment,
Pavel Peleska      Tel:   ++49-89-722-41253
Siemens AG         Fax:   ++49-89-722-28502
SN EBF11           Email: Pavel.Peleska@mch.scn.de
Hofmannstr. 51
81359 Munich
Germany


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