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overwriting ds80c400 interrupt vectors

john boguse

I have been trying to write c code to overwrite the interrupt vectors on the DS80c400 ( to do the same as the following asm code)

EXTRN CODE (com_isr)
MOV DPTR, #000023H
MOV A, #02H;
MOVX @DPTR, A;
INC DPTR;
MOV A, #BYTE2 com_isr;
MOVX @DPTR, A;
INC DPTR;
MOV A, #HIGH com_isr;
MOVX @DPTR, A;
INC DPTR;
MOV A, #LOW com_isr;
MOVX @DPTR, A;

i would like to do the same in 'c' but when I get a pointer to the com_isr fuction it is in the "generic pointer" format which is not much use. So any suggestion on how to do this in C?

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    Two issues:

    1) Your assembly code, as given, won't typicall overwrite the interrupt vector table at all --- not unless you have von-Neumann address decoding in the lowermost address range.

    2) To get a pointer to xdata instead of generic pointer, cast it to a pointer to xdata. Details in the manual.

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  • 0

    Two issues:

    1) Your assembly code, as given, won't typicall overwrite the interrupt vector table at all --- not unless you have von-Neumann address decoding in the lowermost address range.

    2) To get a pointer to xdata instead of generic pointer, cast it to a pointer to xdata. Details in the manual.

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