Very wierd problem

[jswayze]

Hi folks,

I've scratched my head over this one for most of the day and after paring my original program down to the minimal number of lines, I'm still stuck. First, the code:

@ DEVICE INTRC_OSC, LVP_OFF, WDT_OFF, MCLR_OFF

count1 var word

init:
    count1 = 0

check1:
    if count1 = 0 then high 0
--------------
    if count1 = 7 then
high 1
pause 20
low 1
    endif
-------------
    IF count1 = 20 then low 0
     
    if count1 = 100 then
        count1=0
    else
        count1 = count1 + 1
    endif
    
    pause 20                        ' 20 ms increments
    goto check1

This is essentially an LED flasher where I can control the duration and delay of the flashes but substituting different numbers in the "if count1=" lines. Hopefully it's pretty easy to follow. Initially, ignore the "if count1=7 ... endif" lines.

When I run this on my 16F628, I expect to see my LED flash at a constant rapid rate. When count1=0, the LED goes on. When count1=20 the LED goes off. When count1=100 we start all over again.

What actually happens is that as soon as I power up the PIC, I get one flash, a short delay, then the rapid flashes I expect. It's this rogue flash at the beginning that I can't figure out.

Now about the HIGH 1/LOW 1 lines. I added these in to flash a "debugging" LED when count1 reached certain values. What I found was that, for the first cycle only, count1 was being reset when it reached 6! If I leave the code as shown (IF count1=7), the LED at 0 does it's initial wierd flash before running smoothly. If I change it to (IF count1=6), then I get a flash from BOTH LEDs during the first rogue flash.

Can anyone offer any explanation to this? After the first errant flash everything runs fine. I just don't get it.

Thanks for your time,

Jeff