Matthew,

 The first thing I see wrong I believe is that you have the
 "INTERRUPT VECTOR" at 0x03.  It should be 0x04.  Everything
 else looks okay from my initial glance.  I think if you get
 the interrupt vector corrected, it'll work as planned.

                                     Regards,

                                       Jim


>This is a multi-part message in MIME format.
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>  Hi All,
>
>Can someone tell me why the following code will not work. Is this the

>correct way to initilise the timer and use the timer overflow interupt.
>
>Thanks in advance
>
>Mathew Cohen
>
>
>             ORG     H'50'
>
>Start
> Call Initporta
> Call Initportb
> Call Initmr
> GOTO Checkswitch
>
>;------------------------------------------------------------------------

>--
>
>  ORG H'03'
>TmrInterupt
>
> BTFSC PORTB,7
> call Initmr
> goto toggleleds
>
>Initmr
> CLRF TMR0
> BSF STATUS,RP0 ;select bank 1
> CLRF OPTION_REG
> MOVLW B'00000111'
> IORWF OPTION_REG,1
> BCF INTCON,T0IF
> BSF INTCON,T0IE
>
> RETURN
>
>
>Initporta
>
> BSF STATUS,RP0
> MOVLW 0
> TRIS PORTA
> BCF STATUS,RP0
> MOVLW 31
> MOVWF PORTA
>
> RETURN
>
>Initportb
>
> BSF STATUS,RP0
> MOVLW H'FF'
> MOVWF TRISB
> BCF STATUS,RP0
> RETURN
>
>Checkswitch
> BTFSS PORTB,7
> BSF PORTA,4
> BTFSC PORTB,7
> BCF PORTA,4
> GOTO Checkswitch
>
>
>toggleleds
>
> BTFSS PORTA,1
> goto LedsOFF
> BTFSC PORTA,1
> goto Ledson
>
>Ledson
>
> MOVLW 15
> MOVWF PORTA
> CALL Initmr
> GOTO Checkswitch
>
>
>LedsOFF
>
> MOVLW 0
> MOVWF PORTA
> CALL Initmr
> GOTO Checkswitch
>
> END
>
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