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How to use the symbol ?STACK in another file

song liu

In start.a51, there is defined a idata segment ?STACK.

?STACK  SEGMENT   IDATA


Now, in my asm file, I want to use the ?STACK to reset the SP,when using it directly as follows,

mov SP, #STACK-1


but there is an error: "error A45: UNDEFINED SYMBOL"

How can I do it, thanks.

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  • 0 in reply to song liu

    The ISR may need a bit of stack space to save some registers. Preferably, the ISR should not make a lot of function calls requiring extra stack - most often, it shouldn't do any function calls at all.

    Try to allocate static variables for the information needed by the ISR - and for any calls you just have to make from the ISR.

    I recommend that you solve your stack usage problem, instead of continuing to play with the stack. Besides - playing with the stack means that the ISR doesn't need to know the start address of the main app stadck. It must save the stack pointer, before switching to a separate stack. After being done, this is the value that you must restore - not the start address of the stack.

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  • 0 in reply to song liu

    The ISR may need a bit of stack space to save some registers. Preferably, the ISR should not make a lot of function calls requiring extra stack - most often, it shouldn't do any function calls at all.

    Try to allocate static variables for the information needed by the ISR - and for any calls you just have to make from the ISR.

    I recommend that you solve your stack usage problem, instead of continuing to play with the stack. Besides - playing with the stack means that the ISR doesn't need to know the start address of the main app stadck. It must save the stack pointer, before switching to a separate stack. After being done, this is the value that you must restore - not the start address of the stack.

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