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letter field questions in SRIO message

King Wang84623
Intellectual 860 points
Other Parts Discussed in Thread: TMS320C6472

Hi:

as we konw we can't set the letter field in tci6484 while sending a message by SRIO. so that means hardware will write it. does anyone know which value will be set by hardware? does it always 0 or it may be other valuse?

thank you1

  • 0
    TI__Mastermind 43955 points

    Hi King Wang,

    In the SRIO user guide of TMS320C6472/TMS320TCI648x DSP, http://www.ti.com/lit/ug/sprue13j/sprue13j.pdf , page no: 192, Table 125, they described about the possible values of the LETTER field.

    And also, in that document, it is mentioned that the LETTER field is R/W-00; which means this field can be read and write. This field can be set by writing values. The default value is Zero. The possible values it can hold are given in the tabular column Table 125.

    Please do check whether it answers your question. If not, please reply back with more information.

     

    Regards,

    Shankari.

     

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  • 0 in reply to Shankari G
    TI__Intellectual 860 points

    Hi Shankari:

    I am afraid this is not the answer I want.

    the figure you mention is the Queue map for Rx. the question I asked is for Tx. you can read the same document Page 54, Figure 23. it describes a descritpor for Tx. you can find there is not Letter field, only Mailbox is needed.

    so my question is, if DSP send a message, what the letter field it is? can I change the value?

    thank you!

  • 0 in reply to King Wang84623
    TI__Mastermind 23525 points

    King,

    You are correct, in the C64x devices, the SRIO HW assigns the LTR field of the out-going type 11 message.  It assigns the first available, i.e. LTR 0 first, if it is in use, LTR 1, etc.  This approach allows the highest throughput by not stalling the transmitter, though it does give the user a less flexibility.  The C66x SRIO allows either mode, first available or user assigned.

    Regards,

    Travis

  • 0 in reply to tscheck
    TI__Intellectual 860 points

    Travis:

    understand, thanks!