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MOV dbl(*SP(#14)), AC1

michael breen
Prodigy 10 points

I'm using the C55x s/w simulator and trying to verify some 32bit fixed-point arithmetic. I can't seem to find the above MOV instruction in the TI C55x instruction set listing. Can anyone elaborate on what' exactly is being moved into AC1?

Thanks

  • 0
    TI__Expert 8065 points

    Michael,

    The instruction is using "SP direct addressing Mode" which you can find from the section 6.3.2 of the CPU Reference Guide (http://focus.ti.com/lit/ug/swpu073e/swpu073e.pdf)

     

    What it does:

    Stack Pointer (SP) is not modified. The current stack pointer is used as a base pointer. The 16-bit signed constant (K16) is used as an offset from that

    base pointer. So, the instruction will fetch double words (32-bit) from the address pointed by (stack pointer + 14) and move the 32-bit data to AC1. 

    AC1 = *(stack pointer + 14)

     

    Note :

    when address is odd (n = odd), then msw = *n, lsw = *(n-1)

    when address is even (n = even), then msw = *n, lsw = *(n+1)

    Please refer to 3.3 Data Space in the CPU Reference Guide for details.

     

    Hope this helps. 

     

    Regards,

    Peter Chung