Abnormal behaviour PIC18 Simulator IDE v2.81

[robertkendrick]

Hi

Try this simple code using FSR1 with andwf and iorwf instructions.
label one works. label two and three fail.

Wondering if anyone has had similar problems and knows of a fix.

; 18F4520
; abnormal behaviour in PIC18 Simulator IDE
	org 0
	goto 0x100
	
	org 0x100
one:	; works as defined
	movlb 0
	setf FSR1H
	movlw 0x93
	movwf FSR1L
	movlw 0xee
	movwf preinc1

two:	;this code snippet does not alter
	;TRISC and corrupts TRISD. Also
	;FSR1 is incremented twice.	
	movlw 0x93
	movwf FSR1L
	movlw	0x7f
	andwf	preinc1,f

three:	;this code snippet does not alter
	;TRISC and corrupts TRISD. Also
	;FSR1 is incremented twice.		
	movlw 0x93
	movwf FSR1L
	movlw	0x0f
	iorwf	preinc1,f

	end

 

[ericgibbs]

hi,
Would you please post the remainder of the code.?

Lets see the snippets in context.

 

[Ian Rogers]

Eric... I very much think that it.... "org" at the beginning and "end" at well... the end..

 

[robertkendrick]

Eric, thanks for the reply.

I don't have any code I would like you to fix (not today anyway ..)

The posted code illustrates a pretty serious bug in Pic18 Simulator.

Place these five instructions into the Assembler and 'assemble & load'
Then single step them.
TRISC (0x0f94) should be updated by the IORWF instruction but isn't.
TRISD (0x0f95) is corrupted.
FSR1 is incremented twice instead of once.

;This does not alter
;TRISC and corrupts TRISD. Also
;FSR1 is incremented twice.
setf FSR1H
movlw 0x93
movwf FSR1L
movlw 0x0f
iorwf preinc1,f

Do the same assembly and single step in MPLAB (8.70) and it works as expected and documented in the data sheet.

Further tests within PIC18 sim also show that this bug applies to all IORWF/ANDWF instructions whilst using PREINCx with any FSR.