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From C, inline assembly LJMP to Numerical Address

How do I perform a long jump to a numerical address from my C code?
I'm pretty sure I have to do this with inline assembly - however that
seems complicated for C51. I figured in C I could do this:

typedef void (*jmpPtr)(void);
jmpPtr jmp;

...

unsigned int address = 0x4000U;
jmp = (jmpPtr) address;
(*jmp)();

Except for the call differences, I think this would be the same as doing
a jump to the numerical address? Keil, is this correct?

Parents

0 Mark Odell over 24 years ago in reply to Mark Odell

Let's try that again.

Dan, you have inspired me. Here's my "Jump to an absolute address" that I hope solves the "jump from C" issue.

// 'r_' prefix denotes a CPU 'r'egister.
sfr r_stackPointer = 0x81;

void main(void)
{
    // Point so that this will work for 8051's and 52's.
    unsigned char data *p = 0x7E; 

    // Little endian, LSB in lower address, MSB in higher address.
    *p = 0x00;  // LSB of address 0x4000.
    ++p;
    *p = 0x40;  // MSB of address 0x4000;

    // Now fool the CPU (this is the magic part).
    r_stackPointer = 0x7F;

    // "Jump via return"
    return;
}

What fun.

- Mark

Reply

0 Mark Odell over 24 years ago in reply to Mark Odell

Let's try that again.

Dan, you have inspired me. Here's my "Jump to an absolute address" that I hope solves the "jump from C" issue.

// 'r_' prefix denotes a CPU 'r'egister.
sfr r_stackPointer = 0x81;

void main(void)
{
    // Point so that this will work for 8051's and 52's.
    unsigned char data *p = 0x7E; 

    // Little endian, LSB in lower address, MSB in higher address.
    *p = 0x00;  // LSB of address 0x4000.
    ++p;
    *p = 0x40;  // MSB of address 0x4000;

    // Now fool the CPU (this is the magic part).
    r_stackPointer = 0x7F;

    // "Jump via return"
    return;
}

What fun.

- Mark

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