Hi Mathew,

Welcome to the world of PICs.

Try this out for your LED flasher.

        Title    "LED Flasher"
        ;
        list p=16F84    ; processor type

Status  equ 3h          ; Status register
rp0     equ 5h          ; RAM Page select bit
PortA   equ 5h          ; PortA register
Option_Reg  equ 81h     ; option register (in RAM Page 1)
TrisA   equ 85h         ; TrisA register (in RAM Page 1)
intcon  equ 0Bh         ; intcon register
t0if    equ 2h          ; tmr0 overflow flag
Count   equ 0Ch         ; register for delay counting

        org 0h          ; startup vector = 0000

        ; Setup Ports

        bsf Status,rp0          ; (5) TrisA is in RAM Page 1
        movlw b'11111110'       ; set PortA 0 bit as an output
        movwf TrisA
        movlw b'11010111'       ; set tmr0 for internal clock and
        movwf Option_Reg        ; prescale for tmr0 @ 1:256
        bcf Status,rp0          ; (5) back to RAM page 0

        ; main code loop

mnloop  movlw d'20'             ; count delay loop 20 times
        movwf Count
        movlw b'00000001'       ; alternate PortA bit 0
        xorwf PortA

        ; Total delay is approx 1/2 second @ 10MHz

delay   btfss intcon,t0if       ; (2) wait for tmr0 overflow
        goto delay

        bcf intcon,t0if         ; (2) clear tmr0 overflow flag
        decfsz Count            ; count this 20 times
        goto delay
        goto mnloop             ; alternate PortA bit 0 and reset delay count
        ;
        ;
        end

Notice that I defined the Option register as "Option_Reg".
If I defined it with it's real name "Option" then the compiler will
complain because "Option" is an instruction mnemonic. << try typing that
fast :-)

Have fun...

--
Best regards

Tony

http://www.picnpoke.com
Email sales@picnpoke.com