Hi,
please take into account GPIO.3 can not be used as an output pin. It is
simply not capable. BTW, if you BTFS it, then it is o.k. I do not know
what she makes if her TRIS bit is set to 0.

Regards,
Imre


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On Tue, 14 Aug 2001, Kevin Blain wrote:

> your tris is upside down!  0x38 ( b'00111000' ) sets the 1's as inputs and
> the 0's as outputs.
>
> HOT TIP: (well, tip) use binary notation rather than hex for tris type
> commands, the 1s and 0s look like Is and Os too, it's also easier to see
> which pin is which.
>
> You need, b'00000111' or 0x07
>
> Also in loop, you are checking GPIO,3 - should this be a different pin? You
> comment at the beginning says set 0,1,2 as input, but your comment later
> says read 3 as input.........
>
>
> Garage door warming system eh? What luxury! or is that a typo for warning?
>
>
> Regards, Kevin
>
> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Fok, Ben
> Sent: 14 August 2001 16:14
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [PIC]: Need help on PIC12C508A programming
>
>
> I am working on a little project using the 12C508A.  It is a garage door
> warming system.  The Pic is connected to a buzzer and two LEDs (GPIO 2), one
> red(GPIO 0) and one green(GPIO 1).  I want use GPIO 3/MCLR/Vpp for
> detection.  Here is a short program I wrote:
>
> start:          org     0x00
>                 movlw   0x38
>                 tris    gpio            ;set gpio 0, 1, 2 as input and the
> rest as output
>                 movlw   0x3f
>                 option                  ;enable weak pullup and wake on pin
> change, bit 6 and 7
> loop:           btfsc   gpio, 3         ;check and see if gpio 3 is low
>                 goto    loop            ;if not check again
>                 call    buzzer          ;make the buzzer buzz
>                 goto    start
>
> When I program the PIC I use LP crystal, internal MCLR and no watchdog.
>
> The problem I have is gpio 3 is acting as an input pin.  I don't know how to
> debug it because the ICE doesn't emulate that pin.
>
> Please help.
>
> Ben
>
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