Okay, thank you. That's a positive answer, better than I thought. I can accept if uC will behave odd but I don't want to cause permanent damage to it.

I'll leave it up to god to decide if my uC becomes unstable :)

The max sink current in the data sheet is not very helpful in this case - it specifies the sink current at some V(ol)(max) - Voltage, output low, max. It is an indication of the max sink current the device will provide and still give a valid "low" output level.

There is not a spec in the datasheet for the current that will be sunk into a "zero" output which is connected to an arbitrary supply.

The I(ol) spec promises that the chip can drive a valid "zero" into some current - the output driver might meet the spec or be significantly better depending on process variations, temperature, power supply voltages, etc.

Practically the output driver can be modeled as a resistor in this limited case so it won't draw enormous currents if shorted out, but it may pull "up" the local chip ground causing noise problems (meaning data corruption) in adjacent circuits inside the chip.

It is common in production for the occasional solder bridge to short a signal to one of the power supplies. Generally boards work once the short is removed.

I would not expect to blow up the chip, but I wouldn't be surprised if the system doesn't work correctly with the pin driven low while connected to the power supply.

Good luck,
Bill.

-----Original Message-----
From: A... [mailto:A...] On Behalf Of Dan Lyke
Sent: Tuesday, May 19, 2009 10:43 AM
To: A...
Subject: Re: [AT91SAM] Re: at91sam7s PIO set to output 0 but connected to power plane

On Tue, 19 May 2009 14:18:54 -0000
"yeayeah85" wrote:
> Okay, thanks! What did you search on when googling? I can't find any
> useable information.

I searched for "AT91 sink current", but the max current you can sink or
source is also in the spec sheet for your processor (and it's more
reliable if you get it from there).

Dan

On Tue, 19 May 2009 14:18:54 -0000
"yeayeah85" wrote:
> Okay, thanks! What did you search on when googling? I can't find any
> useable information.

I searched for "AT91 sink current", but the max current you can sink or
source is also in the spec sheet for your processor (and it's more
reliable if you get it from there).

Dan

--- In A..., Dan Lyke wrote:
>
> On Mon, 18 May 2009 21:56:03 -0000
> "yeayeah85" wrote:
> > How can I check if I might burn the uC if I switch the pin to output
> > 0 but the pin stays high because connected to power plane?
>
> I don't know what the maximum sink current for the particular pins on
> the particular chip you're connecting to is, but a quick Google suggests
> that the max current you can sink on a pin on an AT91 decice is
> somewhere between 16mA and 200mA, depending.
>
> So, yes, if you have a pin connected directly to Vcc and you drive it
> to 0, there's a good chance you're going to burn something up. This
> would be a good place to put a current limiting resistor.
>
> Dan
>

Okay, thanks! What did you search on when googling? I can't find any useable information.

<>

Hum. I think it's to late ..., isn't it ? ;-)

Eric

-----Mensagem original-----
De: A... [mailto:A...] Em nome de Dan
Lyke
Enviada em: mardi 19 mai 2009 00:25
Para: A...
Assunto: Re: [AT91SAM] at91sam7s PIO set to output 0 but connected to power
plane

On Mon, 18 May 2009 21:56:03 -0000
"yeayeah85" com> wrote:
> How can I check if I might burn the uC if I switch the pin to output
> 0 but the pin stays high because connected to power plane?

I don't know what the maximum sink current for the particular pins on
the particular chip you're connecting to is, but a quick Google suggests
that the max current you can sink on a pin on an AT91 decice is
somewhere between 16mA and 200mA, depending.

So, yes, if you have a pin connected directly to Vcc and you drive it
to 0, there's a good chance you're going to burn something up. This
would be a good place to put a current limiting resistor.

Dan

On Mon, 18 May 2009 21:56:03 -0000
"yeayeah85" wrote:
> How can I check if I might burn the uC if I switch the pin to output
> 0 but the pin stays high because connected to power plane?

I don't know what the maximum sink current for the particular pins on
the particular chip you're connecting to is, but a quick Google suggests
that the max current you can sink on a pin on an AT91 decice is
somewhere between 16mA and 200mA, depending.

So, yes, if you have a pin connected directly to Vcc and you drive it
to 0, there's a good chance you're going to burn something up. This
would be a good place to put a current limiting resistor.

Dan

Hi!

How can I check if I might burn the uC if I switch the pin to output 0 but the pin stays high because connected to power plane?

...
Set PIO to output
Try to pull line low by outputting 0 from uC
Set PIO to input
Read value on PIO
...

How dangerous?

Thankful for any answer!