Lars Johansson wrote

The problem is that when I turn on the power to the circuit,
it's sometimes completly dead. If I
then turn the power on and off a few times, it
(randomly) start's to work again!!??
Snip

The following section of code is part of the startup code for a '57 and I had
a similar iritation until i simulated it with random info in the registers it
somtimes crashed I traced it to the FSR not initalising properly and the
program jumping into the subroutienes and never coming back while trying to
clear the RAM.
Check FSR is cleared before trying to use it.

INIT
        BCF     STATUS,PA0      ; SET TO PAGE 0
        BCF     STATUS,PA1      ; DO IT
        CLRW                    ; CLEAR W TO SET PORTA TO O/P
        TRIS    PORTA           ; TRIS PORTA TO MAKE IT O/P

;the fix for two days headache.....
        MOVWF   FSR             ; FIX FOR FSR B5,6 TO 0 BY SMS 20-1-97

        MOVLW   B'0111'         ; SET CONTENTS OF PORTA
        MOVWF   PORTA           ; DO IT
        MOVLW   B'01111000'     ; SET CONTENTS OF PORTC
        MOVWF   PORTC           ; DO IT
        MOVLW   B'10000001'     ; SET I / O OF PORTC
        TRIS    PORTC           ; DO IT
        MOVLW   .22             ; LOAD LAST RAM REGISTER WITH 22
        MOVWF   LAST_REG        ; DO IT
        MOVLW   MEMBASE         ; LOAD FIRST RAM ADDRESS INTO FSR REG
        MOVWF   FSR             ; DO IT
CLR_REG CLRF    INDF            ; CLEAR THE RAM REG POINTED TO BY FSR REG
        INCF    FSR,F           ; INC FSR
        DECFSZ  LAST_REG,F      ; DEC LAST_REG COUNTER
        GOTO    CLR_REG         ; LOOP BACK UNTIL COUNTER IS ZERO
        CLRF    LAST_REG        ; CLEAR THE LAST_REG LOCATION
        CLRF    FSR             ; CLEAR THE FSR REG