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Serial Rapid I/O - message retry question

B. Bowling
Prodigy 195 points
Other Parts Discussed in Thread: TMS320C6474

Referring to the TMS320C6474 SRIO users guide:

http://www.ti.com/lit/ug/sprug23d/sprug23d.pdf

On page 50, there is a comment that says "single-segment messages will never generate RETRY responses". Is this true in general for single-segment messages? This question came about from a design where there is a SRIO port connection between a DSP and a FPGA direct, and in this setup the need for message retries is not needed. They do not want to have to store messages on the FPGA side to respond to a RETRY.

Any feedback on this?

- Bruce

  • 0
    TI__Mastermind 23525 points

    True.  The DSP will not generate type 11 Retry responses if only single segment messages are received by it.  Two things to remember, first it can still generate Type 11 ERROR reseponses as discussed in section 2.3.4 of the sprug23d.  Secondly, this sentence is talking strictly about logical layer Type 11 responses, not physical layer control symbols.  It is still possible to get a physical layer retry control symbol, similar to a NACK control symbol, these must be handled by the FPGA correctly. 

    Regards,

    Travis