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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

    How could you make "Stack" public/extern, pls tell it in detail

    In the module that has the stack segment just include the line:

    Public  Stack

    And in the module that needs to reference the stack segment do (as you have correctly done):

    Extrn  Idata (Stack)

    Also, I notice your code snippet of:

    mov R0, #Stack;

    If you want to initialise the stack to the base of the block, you would normally use:

    mov R0, #Stack-1

    Because the stack pointer (on the 8051) increments before storing the data byte; sometimes referred to as a pre-increment style stack.

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  • 0 in reply to song liu

    How could you make "Stack" public/extern, pls tell it in detail

    In the module that has the stack segment just include the line:

    Public  Stack

    And in the module that needs to reference the stack segment do (as you have correctly done):

    Extrn  Idata (Stack)

    Also, I notice your code snippet of:

    mov R0, #Stack;

    If you want to initialise the stack to the base of the block, you would normally use:

    mov R0, #Stack-1

    Because the stack pointer (on the 8051) increments before storing the data byte; sometimes referred to as a pre-increment style stack.

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