James & Iliana Holbrook wrote:
>
> Greetings,
>         I've been messing with PIC's for some time but have laid off for the
 last 8
> months while I attend school. School's over so I'm back to PIC'n.
>         My first project is a typical counter using 4 LED's multiplexed, I'm
 using
> PortB for drives and 4 pins of PortA to select the digit that is on. The
> problem is that I can't get the program to see my switch. I've pulled it up
> with a 10k resistor and a logic probe shows a good signal from the switch.
> Funny thing is that if I pull the wire and test the porta pin 4 (RA4) I get a
> pulse signal just like the other pins. I've read the data sheet but my brain
 is
> pretty fried at this time due to intense schooling.
> some snippets from my code follow.
>         Can someone point out my errant ways ? I'm using tris instead of trisb
 or
> trisa because that's the way I learned.
>
> ;------- disp.asm ----------------------
>
>         list    p=16c84
>         radix   hex
>         include "p16c84.inc"
>
> ;------- equates -----------------------
>
>  CBLOCK   0x0C
>         count, count1, count2, count3, count4
>         disp1, disp2, disp3, disp4
>         btn, flag, digit, comm
>         ENDC
>
> #define butn    PORTA, 0x04
> #define zero    STATUS, 0x02
> #define btnflg  flag, 0
> #define incflg  flag, 1
>
> ;------- program code ------------------
>
>         org     0x00
>
> start   movlw   0x00            ; Initialize Portb
>         TRIS    PORTB           ; All Outputs
>         movlw   0x10            ; Initialize Porta
>         TRIS    PORTA           ; 0,1,2,3 are output, 4 is input
>         movlw   b'01110'                ; set so first digit is visible
>         movwf   digit
>         movlw   B'00111111'     ; set to display zero
>         clrf    comm            ; clear counter
> main    movwf   PORTB
>         movf    digit, w
>         movwf   PORTA
>         call    digcnt          ; Call digit count routine
>         btfsc   butn            ; is button down ?
>         btfss   butn            ; is button down ?
>         bsf     btnflg          ; set flag if not
>         btfss   butn            ; test again
>         call    btndn           ; button down routine gets called
>         btfsc   incflg          ; check to see if increment is due
>         call    inccnt1         ; if so then call increment count1
>
>         Thanks for your time !
>                 James Holbrook

Hello james,

I think the problem is that RA4 is an open collector output, i can see
the problem on the PIC 16C63 and several nights of work were necessary
to solve the problem.
For more information see page 2-743 of the PIC 16/17 microcontroller
data book and you will see RA4 is buffer type ST wich is open collector
output.
Nice work.

JEAN-PIERRE