AVR-Chat

I have a couple questions:

1 - What frequency is the PIC running at?

20MHZ


2 - Are the DC input leads to the PIC and the 74HC595 adequately bypassed 
with capacitors? (I'd assume you did this properly).

100NF FOR EACH

3 - Are all ground leads on the PIC grounded? I just about went around the 
bend once trying to figure out why one 16F877 circuit wouldn't work and 
found I'd forgotten to ground one of the ground leads. It worked fine once 
I did that.

ALL GROUND LEADS ARE GROUNDED


4 - What is the duration of the pulses from the PIC to the HC595 that 
you're sending, per your program?

NOT 100% SURE  THERE ARE AT LEAST 10 nop's BETWEEN EACH TRANSITION

This is not my circuit or my code it is a fix up job for a system where the
original designers have quit "ex gone broke".
There are quite a few of these units in the field.
The logic analyser is capable to 50MHZ but on these lines it misses the
pulses and will only pick up a signal when glitch detection is turned on. 
Thanking you,
Owen.


Zack

On Thu, 7 Sep 2006, oldhat_owen wrote:

> I know this is perhaps a bit off topic but I have several boards with 
> PIC16F877 processors driving an HC595 shift register and the output 
> pins from the pic driving the HC595 are virtually all glitches.
> 
> It is hard to pick up a high or low as such on the logic analyser 
> other outputs seem ok, has anyone any idea what may be causing this. 
> 
> And yes I do not like pic's I normally use AVR'S.
> 
> Owen.
> 




 
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