Thread: saving an address in two bytes

Originally Posted by afflictedd2

stackPointer is:
unsigned char* stackPointer;

Yep, I'm dropping at the assembly level.
I need to load the stack once I return from interrupt, and that's why I need to put the address of the function in the first two bytes, in the program counter of the stack.
Here's a picture of the stack:
http://www.owlnet.rice.edu/~elec201/...ges/img190.gif

Ted.

Gotcha! and here's howto store the address of the function byte-wise

Code:

#include <stdio.h>

void f(void) {}

int main(int argc, char *argv[])
{
    void (*pf)(void);
    unsigned char *sp, t;

    pf = f;

    /* store lo byte */
    t = (unsigned) pf & 0xff;
    sp = (unsigned char *) t;

    /* store hi byte */
    t = (unsigned) pf >> 8;
    sp = (unsigned char *) t;
}

You should be able to simply use

Code:

*(unsigned*)(stackPointer-1) = (unsigned)your_function;

providing stackPointer points to "SP before interrupt" from your picture.
If the stack pointer points to "SP after interrupt" use (stackPointer+8)