Program Counter

[GARTHWILSON]

True, and you're reminding me of why I abandoned my quest for relocatable code on the 6502-- code that could be scooted around in memory after it was loaded and may have already been running. It wasn't so much the code location that was the problem as the data location. It can still be done, but it was getting too cumbersome to be worth it. If you have some slick ideas though, I might take it up again.

[kc5tja]

dcl raises a point that I didn't consider at the time. However, if you're willing to invest in using 5 bytes of zero-page at a fixed (or linker-patched) address,

Code: Select all

.proc whereAmI
  ldx #3
again:
  lda thunk,x
  sta zpThunk,x
  dex
  bpl again
  jsr zpThunk

thunk:
  pla
  tax
  pla
  rts
.endproc

You have to JSR to whereAmI -- JMPing to it will likely cause a crash.

[dclxvi]

I've added Where-Am-I routines to the wiki at:

http://6502org.wikidot.com/software-whereami