Thanks John,

I Believe it is blaintly obvious that I am a complete newby to this. Trying
to run before I can walk.
Can you also tell me weather I have to enable the global interupt bit before
the timer overflow interupt will work.


Thanks again

Mathew Cohen
mathew@everythingit.net

----- Original Message -----
From: John Considine <jconsi@MAGICNET.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Wednesday, October 27, 1999 12:41 PM
Subject: Re: Why doesn't this code work ???


> The PIC16C84 has the interupt at org 4
> I don't see you saving the registers after going into interupt and
returning
> the registers when returning (you should have a RETFIE, not a return)
> _w    equ    10
> _status    equ    11
>
> org 4
> Interrupt
> movwf    _w                ;save work
> movf     STATUS, w
> bcf        STATUS, RP0    ;puts the pic register in a know page (optional)
> movwf    _status        ;save status
>
> bcf    INTCON, 1    ;clear INTF in INTCON register
> bcf    INTCON, 2    ;ckear TOIF in INTCON register
>
> Do your other interupt code here
>
> RETFIE                    ;puts the PC at Top of Stack (where the interupt
came
> from)
>
>
>
>
>
> Mathew Cohen wrote:
>
> > I believe that this is the interupt vector location for the 16f84. In
> > software simulation it seems to work. If this is not the case than could
> > someone please set me straight. Also it ahs been brought to my attention
> > that I seem to have left the global interupt bit low this is probably
why
> > the code does not work .
> > Can someone test it thanks.
> >
> > Regards
> >
> > Mathew Cohen
> >
> > ----- Original Message -----
> > From: Martin Schdfer <Schaefer@ELEKTRONIK21.DE>
> > To: <PICLIST@MITVMA.MIT.EDU>
> > Sent: Wednesday, October 20, 1999 10:21 PM
> > Subject: Re: Why doesn't this code work ???
> >
> > > Hi Mathew,
> > >
> > > why is your interrupt starting at H'03' ?
> > >
> > > Mathew Cohen schrieb:
> > >
> > > >   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
> > >
>