I have recently made a successful debugging on one my very long program, consisting of about 8000 lines, producing cca 12 kb long code. The problem was that sometimes, if it was overflooded with data, it got stuck somewhere. It was of course very important to find out where.

First thing I noticed was that it was not reset by the WDT, it meant that the WDT counter got reset command regularly. I came to the idea to switch WDT off, and do a replace in the Editor: all places of reset WDT were replaced by word DEBUG. Then I defined the following macro

DEBUG	MACRO
	JB	Port.Pin,$+6
	CALL	SENDME
ENDM

.
The routine SENDME was something like this

SENDME:	MOV	R1,#80H

	POP	A	; Higher
	MOV	@R1,A
	POP	A       ; Lower
	INC	R1
	MOV	@R1,A

	DEC	R1
	INC	SP
	INC	SP

	CALL	ASCHEX  ; Transform the value to 2 chars and send
	INC	R1
	CALL	ASCHEX

	mov	sbuf,#' '
	jnb	ti,$
	clr	ti

	RET

So, I soldered a taster on a free Port.Pin, and when it got stuck again, I got the address on the screen ! (By connecting it to a port pin and not to, say, external interrupt, you need not think whether and which interrupts are enabled).

Of course, you can easily modify the routine and make it send something else: DPTR, some register or memory contents ... And no problem to place DEBUG somewhere else in the located part of the program !

I really appreciate your great work ! Good luck !

Slobodan