AVR (atmega8515) rjmp doesn't jump relatively

Question

Relative jump to an address within PC - 2K +1 and PC + 2K (words). In the assembler, labels are used instead of relative operands. For AVR microcontrollers with program memory not exceeding 4K words (8K bytes) this instruction can address the entire memory from every address location.

Based on http://www.atmel.com/webdoc/avrassembler/avrassembler.wb_RJMP.html , the rjmp command should change the PC register relatively. But my code below are jumping to the exact address (in this case to ldi temp, low(RAMEND) command with address 0x00)

.include "m8515def.inc"

.def temp = r16


STACK_INIT:
    ; init stack pointer
    ldi temp, low(RAMEND)
    out SPL, temp
    ldi temp, high(RAMEND)
    out SPH, temp

TES:
    rjmp 0x00

END:
    rjmp END

I've tried to change the rjmp command to jmp but the atmega8515 doesn't support that command

I don't know if this because of the configuration or something. I'm using AVR Studio 4 for build and run my program. Can anybody explain about it?

David Grayson David Grayson · Accepted Answer · 2017-05-22T19:34:38

This is expected. For the convenience of assembly language programmers, the rjmp operation takes an absolute address instead of a relative one. The absolute address will be converted to a relative one when it actually compiles the binary machine code, and you'll get an error if the address is too far away to jump to.

By the way, you can use the $ symbol in your operands. It is the address of the current instruction. So something like rjmp $+2 would jump to two bytes past the next instruction.

AVR (atmega8515) rjmp doesn't jump relatively

1 Answers