Hi Graham,

Mask out

;         movfw   0x1ff         ; remove this line, the W is automatically
loaded.
          movwf   OSCCAL          ;Set oscillator calibration reg. ( let
this be there )

Regards

Pailoor

Graham North wrote:
>
> 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

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