Merging of two 32-bits to form one 64-bit data

[Ajit Khaparde <akhaparde@platysindia.com>]

PCI Designers,

I have come across a situation during the design of a 66MHz 64-bit PCi-to-PCI Bridge and it goes this way....

Case:
The Initiator on the Primary/originating bus could be a 32-bit master and the Target on the Secondary/Destination bus could be a 64-bit device. Then is it possible to latch the data from the initiator as it is being sent(32-bit) and merge two such 32-bits of data into one to form one 64-bit of data and send it to the target, for it can accept a 64-bit transaction.

I would like someone to comment on this and inform me whether this can be done?

If yes, then I have come across one difficulty.
If the Initiator on the primary side has sent an odd number of Double words then my idea of merging the two 32-bits of data to one single 64-bit could result in merging the last odd 32-bit of data with a null or stale data.

Can someone suggest me a solution for this situation?

Thanks in advance.
Regards,
Waiting for your reply,

Ajit Khaparde
Platys communications (India) Pvt. Ltd.
Design Engineer,
#501, Arien Apartments,
Punjagutta,
Hyderabad-500082,
India
Ph:+91-40-6507141

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