Spehro Pefhany wrote:
> At 10:03 AM 3/17/2004 +0200, you wrote:
>
>>
>> Hi,
>>
>> For the display of my project I'm using four seven segment displays
>> (common
>> anode), using 8 IO pins for the segments, and another 4 to drive the
>> individual displays. The four displays are driven through a BC557
>> transistor
It would seem I was hasty with my suggestion of timing the led "on"
time, due to it being some months since I did it.
I have dug out some of the code, and reproduce it here.
All those with more experience ten ine welcome to pull it to bits.
Regards
Howard
  led_lookup
;----------
;
;rb7=d, rb6=c, rb5=e, rb4=g, rb3=f, rb2=a, rb1=b, rb0=interrupt
        addwf   pcl,f   ; Jump into the correct location
;                 dcegfab(int)
        retlw   b'00010000'     ;       0
        retlw   b'10111100'     ;       1
        retlw   b'01001000'     ;       2
        retlw   b'00101000'     ;       3
        retlw   b'10100100'     ;       4
        retlw   b'00100010'     ;       5
        retlw   b'00000010'     ;       6
        retlw   b'10111000'     ;       7
        retlw   b'00000000'     ;       8
        retlw   b'00100000'     ;       9
        retlw   b'11111110'     ;       blank
;--------------------------------
        ;seven segment patterns, based on clear to light segment
        ;so segments not lit are set
        ;bits 1 to 7 are for leds
        ;bit 0 not used for leds, it's the wheel interrupt
        ;NOTE!!! So as not to have to fuck with the upper PC byte
        ;this routine must be in the first 256 bytes of prog memory
;----------------------------------
;-------
;       RA0 is thous driver, RA1 is hunds, RA2 is tens, RA3 is units, ; RA5 is
Dec'Point
;       0 bits are switched on.  1 bits are switched off
;       dpflag is set to show dec point
;--
        call    timer0          ;start timer
        movfw   units           ;load with units digit
        call    led_lookup
        movwf   led_segs        ;copy to led_segs
        movlw   b'000111'       ;default decimal point on
        btfss   dpflag          ;skip to show decimal point
        movlw   b'100111'
        movwf   porta
        call    timer_end       ;wait for timeout
;--
        call    timer0          ;timer stops "leakage" between digits.                          ;slows multiplexing
        movfw   tens            ;load with tens digit
        call    led_lookup
        movwf   led_segs        ;copy to port b (bit7 will be zero                                              ;because digit
is always 9 or less
        movlw   b'001011'       ;default decimal point on
        btfss   dpflag          ;skip to show decimal point
        movlw   b'101011'
        movwf   porta
        call    timer_end       ;wait for timeout

        ;keep going for the rest of the digits

;--------
;---------------
timer0
;---------------
                                ;set for one millisecond
        bcf     intcon,t0if
        clrf    tmr0
        return
timer_end
loop02  btfss   intcon,t0if
        goto    loop02
        return
;--------------------------------

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