4.6.3 Location Counter

The current location within the active program section is accessible via the symbol $. This symbol expands to the address of the currently executing instruction (which is different than the address contained in the program counter (PC) register when executing this instruction). Thus:

goto $   ;endless loop

will represent code that will jump to itself and form an endless loop. By using this symbol and an offset, a relative jump destination can be specified.

Any address offset added to $ has the native addressability of the target device. So, for baseline and mid-range devices, the offset is the number of instructions away from the current location, as these devices have word-addressable program memory. For PIC18 instructions, which use byte addressable program memory, the offset to this symbol represents the number of bytes from the current location. As PIC18 instructions must be word aligned, the offset to the location counter should be a multiple of 2. All offsets are rounded down to the nearest multiple of 2.

For example:

goto	   $+2   ;skip...
movlw	  8     ;to here for PIC18 devices, or
movwf	  _foo  ;to here for baseline and mid-range devices

will skip the movlw instruction on baseline or mid-range devices. On PIC18 devices, goto $+2 will jump to the following instruction; i.e., act like a nop instruction.