From: "petrus bitbyter"
Subject: Re: 8051 clock
X-Newsreader: Microsoft Outlook Express 5.50.4807.1700
Date: Sat, 05 Oct 2002 11:57:53 GMT
NNTP-Posting-Date: Sat, 05 Oct 2002 13:57:53 MET DST
Organization: chello broadband
Do you really have a 8051 or is it a 8031? A 8051 is a mask rom version and
can only be used in a circuit that has been developed for it. Putting it in
another circuit will give unpredictable results, including clock failure.
Assuming you have a 8031, I understand the clock does not work on your
board but it does outside your board with only C's, X-tal and power
You may have a defective processor. You can try another one but the fault
may be caused by your circuit. So may end up with two defective processors
and the certaincy you have a faulty circuit.
More likely you have a fault in your circuit, most likely a short.
- Check the unpowered, unconnected circuit for shorts. All pins of the
processor may cause the problem. Check for ground shorts as wel as for Vcc
shorts. Do it with and without the processor inserted. Needless to say that
any short, open or other value that cannot be explained by your circuit is
considered suspicious and needs further investigation.
- Your last chanche: Strip everything from your board. The 74373, the eeprom
and all connections to to the processor. Of course except clock and power.
If your clock still does not run, you can be sure there is a fault in your
board. Otherwise you can start to connect the pins - one at a time - until
you find the fault or until everything is ok.
"Eitan Herman" schreef in bericht
> Well i have problem with 8051 clock,
> i had connected the 2 small capacitors ~15nP but still no clock,
> BUT , when i'm taking the 8051 out from the circuit and connecting
> those caps with the vcc,GND i can see the clock as it should be.
> my circuit is simple 8051,74373 and eeprom(at28c64), how can the
> circuit cause me to loose the clock..?? (i check all the connections
> the relevan to the clock)..
> Please your advice,
> Eitan Herman.