Harold Hallikainen wrote:
>
>         Although more complicated on the software side, you COULD
> multiplex the LEDs so  it would take 7 lines to drive the segments plus
> one line to drive each digit (assuming you have high efficiency LEDs so
> the PIC can drive seven segments simultaneously, or you'll look at the
> thing in the dark).  Also, multiplexing can get a bunch of buttons into
> the PIC with fewer wires.
>         If you want to take a hardware approach (recalling that the ideal
> design has zero parts), you might look at the CD4511.  This is a 7
> segment latch decoder driver.  You feed it 4 lines of BCD and strobe a
> latch line and it'll hold it.  You can then share the 4 bcd lines and
> have individual digit strobe lines.

Another solution, other than multiplexing is to use shift registers.
Having two 74HC164 in series could only use 2 pins. Making the shift
fast enough will trick the eye to see the shifting of data. I think it
is easier on the software side.

Here is the routine to send data serially to 2 74HC164.

;data is in led1 and led2, this routine is untested.

datasend:
        movlw   .16             ;16 bits to send
        movwf   count           ;
loop    bcf     PORT,CLK_LINE   ;clear clock line
        rlf     led1            ;shift data to carry flag
        rlf     led2            ;
        bcf     PORT,DATA_LINE  ;assume data is low
        skpnc                   ;skip if low
         bsf    PORT,DATA_LINE  ; data is high
        bsf     PORT,CLK_LINE   ;pulse clock line high, transition occurs here
        decfsz  count           ;
         goto   loop            ;

Regards,
Reggie