I am have problems with a simple program to make leds flash with a 508.  The
program simulates correctly, but when programmed the chip does nothing.

Please can someone help me, it is probably something simple but I can not
see for looking!

Graham

Here is the code:


        list    p=12c508
        include "p12c508.inc"

        radix   dec

        __FUSES _MCLRE_OFF & _CP_OFF & _WDT_OFF & _IntRC_OSC

        cblock  0x07    ;Store variables above control registers

        TICKS
        RTCC

        endc

        org     0x00            ;Start of code space

SAME    equ     1

Led1    equ     0       ;LED 1 connected to GP bit 0
Led2    equ     1       ;LED 2 connected to GP bit 1

;************************** Main ********************************

        movfw   0x1ff
        movwf   OSCCAL          ;Set oscillator calibration reg.

start
        movlw   b'11000010'     ;Set TMR0 prescaler = 1:8 (f_osc=4MHz)
        option                  ;/

        movlw   b'00000000'     ;Make all port bits outputs
        tris    GPIO            ;/


Again                           ;do
        bsf     GPIO,Led1       ;  Led1 on
        call    Wait_1sec       ;  Wait one sec
        bcf     GPIO,Led1       ;  Led1 off
        call    Wait_1sec       ;  Wait one sec
        bsf     GPIO,Led2       ;  Led2 on
        call    Wait_1sec       ;  Wait one sec
        bcf     GPIO,Led2       ;  Led2 off
        call    Wait_1sec       ;  Wait one sec

        goto    Again

;----------------------- SUBROUTINES -----------------------

Wait_1sec
;One second delay subroutine
;Generates delay by calling 5ms delay 200 times

        movlw   .200            ;Init counter for 1 sec
        movwf   TICKS

One_less                        ;do
        call    Wait_5ms        ;  wait 5 ms
        decf    TICKS,SAME      ;  decrement counter
        btfss   STATUS,Z        ;while (count<>0)
        goto One_less
        return

Wait_5ms
Delay subroutine using the timer, 4Mhz Xtal, 32 prescaler
Generates a delay of 5ms if Rtcc preloaded with 100

Wait_5ms                        ;do
        movlw   .100            ;  Rtcc = 225
        movwf   RTCC
Timer_check                     ;do
        movf    RTCC,W          ;  read Rtcc
        btfss   STATUS,Z
        goto    Timer_check     ;while (Rtcc<>0)
        return


        end