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PICList Thread
'[PICLIST] [pic] ICE- funny simulations and volatil'
2001\07\18@070056 by nrad Labuschagne


Anybody working with an MPLAB ICE system, have you ever had the following

environment:    standard breadboard with switchmode psu (5.1v) working on an
lcd project
pic simulated:  16f873 (16xko module)

And this is what's happening

1.Waveforms output on let's say portb viewed with a scope, the duty cycles
are perfectly seperated, but the horisontal lines are rippled really badly.
2.In other instances a pin should be kept at 5v or 0v, but it just floats
around with a very noise 2v p-p random noise wave.
3.Even the 5v line from the pod is full of noise.

This is so bad not even my lcd project wants to work properly and it just
draws black boxes and 1's on the first line. I thought I could have a power
problem and my AC power is at around 227v-230V moving around there. But my
worst fear is my ICE system being stuffed because I don't understand these
random waves being present at pins I expected to be constant at 0 or 1 . I
would expect the power supply of the ICE to be stable. But if the ICE is
damaged, how can I properly be sure, and even worse, what could have
happened to cause this, I didn't put terrible voltages on it at all. It was
working fine this morning and then I did some button inputs on porta, and
since then --- this noise all over the signals.

Anybody have a suggestion?

-- hint: The PICList is archived three different
ways.  See for details.

2001\07\18@170942 by Mike Mansheim

> Anybody working with an MPLAB ICE system, have you ever had the...

Remote possibility:
The ICE lets you choose where it's power (and clock) will come from:
either the emulator itself or the target board.  It requires about
100ma, which some target boards are not equipped to handle.  I'm
not an EE guy, so I don't know what a "standard switchmode psu" is
capable of, but perhaps you have target board power selected and
your power supply is struggling.

By the way, the random noise wave sounds kind of like what I get
when scope probes are hanging in air or or touching oddball things.
Are you sure your probes are healthy and properly connected?  For
these pins where you are expecting a constant 1 or 0, is the
behavior in software also flaky?

-- hint: The PICList is archived three different
ways.  See for details.

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