Re: uP/uC Floating Pins?

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Re: uP/uC Floating Pins?

Michael A. Terrell	11 Mar 2010 23:55
> >> Read the data sheet. > [quoted text clipped - 5 lines] > Ask the guy who told you about the chip? > Use another chip. Jim designs chips. There are no data sheets until the designs are complete. Signature Lead free solder is Belgium's version of 'Hold my beer and watch this!'

Hal Murray	11 Mar 2010 22:11
>> Read the data sheet. > What if it hasn't been written yet? Why are you designing something for a chip that doesn't exist? Ask the guy who is trying to sell you the chip? Ask the guy who told you about the chip? Use another chip. Signature These are my opinions, not necessarily my employer's. I hate spam.

Michael A. Terrell	11 Mar 2010 20:25
> >I guess I could be driven by an I/O pin. Is it possible to program > >those as a "LOW" during POR? > > Read the data sheet. What if it hasn't been written yet? Signature Lead free solder is Belgium's version of 'Hold my beer and watch this!'

Hal Murray

11 Mar 2010 19:28

>I guess I could be driven by an I/O pin. Is it possible to program
>those as a "LOW" during POR?

Read the data sheet.

In general, the junk I/O pins float. You can't "program" them
from software during reset because the software isn't running yet.

Some chips look at a few input pins to select a mode. Some modes
might drive some pins.

The normal trick is to add a weak pulldown if you need a
particular floating signal to be low during reset.

Signature

These are my opinions, not necessarily my employer's. I hate spam.

Jim Thompson

11 Mar 2010 19:11

>> When a uP or uC is exercising its POR cycle, what are the states of
>> the output pins? Floating, or held low, or what?
[quoted text clipped - 4 lines]
>You do mean _output_ pins, not general purpose I/O that might be
>configured for either input or output -- right?

I guess I could be driven by an I/O pin. Is it possible to program
those as a "LOW" during POR?

...Jim Thompson

The only thing bipartisan in this country is hypocrisy

Tim Wescott

11 Mar 2010 17:07

> When a uP or uC is exercising its POR cycle, what are the states of
> the output pins? Floating, or held low, or what?
>
> Particularly if it's recovering from a brown-out that caused POR to be
> exerted.

You do mean _output_ pins, not general purpose I/O that might be
configured for either input or output -- right?

Signature

Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

Jim Thompson

11 Mar 2010 16:42

When a uP or uC is exercising its POR cycle, what are the states of
the output pins? Floating, or held low, or what?

Particularly if it's recovering from a brown-out that caused POR to be
exerted.

...Jim Thompson

I love to cook with wine. Sometimes I even put it in the food.

Re: uP/uC Floating Pins?

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