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what do we read from the CSIDR on a chip where it is not implemented (labelled as Reserved)?

Serge Malouin1
Prodigy 120 points
Other Parts Discussed in Thread: TMS320VC5409A

Hello,

I am trying to detect at runtime if the DSP on the board is a TMS320VC5409 or its replacement the TMS320VC5409A.

The CSIDR (MMR Address of 003Eh) is implemented on the 5409A and has a CHip ID of 0x09.

It is not implemented on the 5409, 003Eh is simply labelled as "Reserved"

What will be returned if I read it on the 5409?

  • 0
    TI__Genius 12575 points

    Hi,

    The datasheet will not specify anything about values you get by reading the reaserved bit, as these is a reserved bit (and not supposed to be written or read).

    I am not sure whether this approach trying to detect the device is the right one.

    Regards

     Vasanth

  • 0 in reply to Vasantha K
    Prodigy 120 points

    What would be the right approach to differentiate between the 5409 and the 5409A?

    The detail that kills us is the division factor in the BSCR that is different between the 5409 and the 5409A. So it we do the same things for both chip, we end up with a 5409a that runs at 1/4 of the speed of the 5409.