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From: John Popelish
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X-Mailer: Mozilla 4.7 [en] (Win98; U)
Subject: Re: 8051 clock
Date: Mon, 30 Sep 2002 21:12:53 GMT
NNTP-Posting-Date: Mon, 30 Sep 2002 17:12:53 EDT
Eitan Herman wrote:
> i connected crystal (3.57Mhz) with 2 small capacitors(800pF) wire like this:
> | |
> | |
> 19 18
> i can see vcc on pin 18 and something like 1.2 volt on pin 19.
> no clock showing(checked with scope).
> 1.what should i do (or what's wrong- need smaller cap?)
> 2.how can i solve it.
> 3.can i use low 555 clock for testing?
> thanks in advance,
> Eitan Herman.
I think your caps are way too big. Something in the 20 ot 47 pf might
work better. The crystal manufacturer should have specific
recommendations. There is also something worrisome about that Vcc on
pin 18. The voltage on the two pins should be roughly the same when
nothing is connected to 18 or 19. The chip may have a blown input.
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