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Start stability

 
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Joined: 23 Aug 2005
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Start stability
PostPosted: Sat Jan 19, 2008 12:42 am     Reply with quote
Hi, Im wondering about how to get the most stable start for a PIC.
In one application a pic 12F635 must start very quickly, as soon as there are a VCC it must start the program. Im using the internal oscillator. The problem seems that at the very beginning there is some "scrambling" at the out ports, it seems to happend to about maybe 1mS. I suppose its natural, but whats the best way to avoid (minimize) it? is it better to use the out ports as drivers or to sink? Im also having a mos-fet at the pin out driving the load, would it be better with some sort of a fast transistor?
By attaching a cap about 1u to the out pin it got better.
The problem can also come from the 5V regulator, I do use a ultra fast one, but..
Anyone have some ideas?
Thanks/
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Joined: 06 Sep 2003
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PostPosted: Sat Jan 19, 2008 11:48 am     Reply with quote
Quote:

I'm using the internal oscillator.
The problem seems that at the very beginning there is some
"scrambling" at the out ports, it seems to happend to about maybe 1mS.
I'm also having a mos-fet at the pin driving the load.

By attaching a cap about 1u to the out pin it got better.

1. Post your #fuses statement.

2. Post your #use delay() statement.

3. Also, post the first part of your code in main(). I want to see how
soon you initialize the i/o pins. Do you have any delay statements
before you set the i/o pins to become output pins ? Do you call
any other routines that have delays in them, such as lcd_init() ?
(The i/o pins start as inputs, after power-on reset.)
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