[ixp1200] SRAM commands queuing

[Yan Luo]

Hi,

I am interested in the SRAM command issuing and queuing in the SRAM
functional unit.
The hardware ref manul talked about how the command bus arbiter select
commans from the command FIFOs. However, the exact timing is not stated in
docs. For example, why does it take 3 cycles from issuing a sram reference
command to enqueuing the command to the functional unit (as seen in the the
thread history window) ? Also, it seems that removing a command from the
SRAM queue cannot be done every cycle. It takes at least two cycles to
dequeue the next command. Is it because the core and the sram bus operate at
different frequency? I use IXP1200 now, I wonder how these parameter are
different in IXP1200, IXP2400 and IXP2800?

Could anyone please explain it or refer me to some useful documents? Any
input will be appreciated.

Thanks,
Yan
--
Yan Luo
Dept. of CSE, Univ. of California
Riverside, CA 92521, USA
http://www.cs.ucr.edu/~yluo/