AVR-Chat

With the talk about JTAG, and I'm definantly new as you will see by 
the question, but won't JTAG make those pins on the micro useless for 
anything but JTAG and ICE use?

Yes and it's well worth it. Have a look at the data sheet to see how 
many (few) pins you loose doing JTAG and DW.

    Sander

stereotyperjack wrote:

>
> With the talk about JTAG, and I'm definantly new as you will see by
> the question, but won't JTAG make those pins on the micro useless for
> anything but JTAG and ICE use?
>
> _

At 10:28 AM 20/03/2008, you wrote:
>but won't JTAG make those pins on the micro useless for
>anything but JTAG and ICE use?

Pretty much so during debug. Once the debug is finished (is it ever?)
you can use them for things like LEDs or DIL switches as you may be
able to fake these during debug.

For instance a run or fault LED(s) could use one of those pins in the final
product. A module address selection DIL switch could also use those pin as
you could fix the module address for debugging.

If I can help it a don't use them for anything else.

DW is easier as it only uses the reset pin.

The new PDI (programming and debugging interface ??) will use only
the reset pin and a dedicated test pin in some of the newest devices.



Regards

John Samperi

********************************************************
Ampertronics Pty. Ltd.
11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA
Tel. (02) 9674-6495       Fax (02) 9674-8745
Email: john@ampertronics.com.au
Website  http://www.ampertronics.com.au
*Electronic Design * Custom Products * Contract Assembly
********************************************************

On Mar 19, 2008, at 6:28 PM, stereotyperjack wrote:

> With the talk about JTAG, and I'm definantly new as you will see by
> the question, but won't JTAG make those pins on the micro useless for
> anything but JTAG and ICE use?


Yes, but using JTAG is optional. Is easier to not use JTAG on a part  
that has it than to need it on a part that doesn't have it.

If one really must have those pins then one can debug everything else,  
disable JTAG, then finish the project.

--
David Kelly N4HHE, dkelly@HiWAAY.net
========================================================================
Whom computers would destroy, they must first drive mad.

Thanks for the input. And I guess 5 pins isn't such a bad trade off.

       
---------------------------------
Never miss a thing.   Make Yahoo your homepage.

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5 pins?  Doesn't JTAG only use four I/O pins, plus VCC, GND and RESET?
Isn't that correct?   Steve

From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of J C
Sent: Wednesday, March 19, 2008 9:25 PM
To: AVR-Chat@yahoogroups.com
Subject: Re: [AVR-Chat] JTAG

 

Thanks for the input. And I guess 5 pins isn't such a bad trade off.

---------------------------------
Never miss a thing. Make Yahoo your homepage.

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[Non-text portions of this message have been removed]

At 03:56 PM 20/03/2008, you wrote:
>5 pins?  Doesn't JTAG only use four I/O pins, plus VCC, GND and RESET?
>Isn't that correct?   Steve

Spot on. :-)

Actually reset is not really needed UNLESS you plan to disable JTAG
in code for, then it is needed to regain control of the chip. I use
it anyway.

Regards

John Samperi

********************************************************
Ampertronics Pty. Ltd.
11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA
Tel. (02) 9674-6495       Fax (02) 9674-8745
Email: john@ampertronics.com.au
Website  http://www.ampertronics.com.au
*Electronic Design * Custom Products * Contract Assembly
********************************************************