68300

At 04:57 PM 10/10/2002 +0100, you wrote:
>Hello All
>This is a general question about SPI operation, and QSPI on the CPU32 in
>particular.


>My question is:-
>How is the slave's response data transferred into the CPU32?

As the data is being clocked out of the CPU32, the data from the slave is 
being clocked in to the CPU32. They happen at the same time.

>The problem I have is that the CPU32 does not know when the response data is
>likely to start or how many bytes there are to be transferred.
>Can the QSPI in the CPU32 be set up to do this - i.e. set/maintain the
>slave's chip active and drive the SPI clock during this "read" part of the
>transaction.

You have to write yourself a protocol.
1) The master sends a request to the slave, the slave sends back idle words.
2) The master sends idle words, the slave sends a message indicating how 
many words are to follow.
3) The master sends idle words, one for each word in the message, the slave 
sends the requested data back to the master.
4) The master sends a thank you words, the slave sends an idle words.
5) The master sends an idle word, the slave sends a you're welcome word

The bigger problem comes in where the QSPI has a 16 word queue. It would be 
really convenient if the transactions were 16 words or less or else you 
have to buffer and reconstruct.

Andrei

>Cheers
>-
>Robert Manktelow
>Telspec Europe Ltd, Rochester, ME1 3QU
>Phone +44 (0)1634 687 133 extension 2346