Keith L. Kovala wrote:

> I've been working with a program to drive a multiplexed (4
> char) 7 segment LED using simple delay routines, now trying
> to get it to trigger off a timer interrupt like used in AN557.


Hi.

Just a few notes about your source...

> InitPorts
>                 bsf     STATUS,RP0              ;select page 0
>         clrf    TRISA                   ;make RA0-4 outputs
>         clrf    TRISB                   ;make RB0-7 outputs
>                 bcf     STATUS,RP0              ;select page 0
>         clrf    PORTA                  ;make all outputs low
>         clrf    PORTB                  ;       /
>                 clrf    Count
>                 clrf    DTEMP
>                 clrf    DTEMP2
>         return

The "select page 0" comments seems wrong (at least one of them)

What is "rtcc". You have references to that term, but no definition or
description.

> InitTimers
>         clrf    MsdTime                 ;clr timers
>         clrf    LsdTime                 ;       /
>                 bsf     STATUS,RP0              ;select page 0
>                 bsf             INTCON, GIE
>                 bsf             INTCON, TMR0IE
>         movlw   B'00000100'             ;assign ps to rtcc
>         movwf   OPTION_REG               ;ps = 32
>                 bcf     STATUS,RP0              ;select page 0
>         movlw   .250                    ;preload rtcc
>         movwf   TMR0                    ;start counter
>         retfie

The "select page 0" comments seems wrong (at least one of them)
Why "retfie" ? You are "calling" this routine. Should be "return".

> ServiceInterrupts
>         .
>         .
>         .
>         retfie
>                 return

Why the "return" here ?



Best Regards
Jan-Erik.

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