JTAG ICE and I/O design

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Hello
Is there any special care needed when using jtag ice
and port c has been used as inputs with external pull-up resistors? I understand that I will not be able to debug portC. Should I add jumpers to isolate my opto coupler and the pull-up resistor when jtag ice is in use?
Thank you
Don

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I do use 1K (or higher) resistors in series with the JTAG pins to drive leds which are not needed during debug. You can debug the other 4 pins of portc but not the JTAG pins during debug.

I have a debug flag so that JTAG gets disabled if I need to see those 4 pins in action, again usually to drive status leds. In my current project I use 2 of the JTAG pins for jumpers, one a the future bootloader and one to disable some functions of the board. In debug mode I fake the inputs with a variable.

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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Hi John
Ok, I like the ideas and your uses. I'm gonna use PortA to drive a ULN2803. On PortC I'm going to use 8 opto couplers to read the status of device in the real world. I will add 1k resistor in series between PortC and my jtag interface for my jtagice. I was looking at your web site. Really neat things there.
Thank you
Don Biederman
Chicago,Il USA

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Quote:
Really neat things there.
:oops: Thanks. The website really needs an update when I get A-ROUND-TUIT, get rid of the old Motorola stuff and replace them with the newer AVR models, freshen up schematics etc. Fortunately I'm too busy to do it, but this year may be the year that I could have lots of free time. Who knows what will happen with the economy.

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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Hi John
When using JTAGICE with the ATMega16 is it possible to set the crystal frequency so I can view the stop watch and cycle counter? I have a 6 Mhz external crystal on my target board would that be a Med or high frequency in the fuse setting?
This is sure a old thread but I'm working on a new project and trying to debug output compare.
Thanks
Don

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Quote:
When using JTAGICE with the ATMega16 is it possible to set the crystal frequency so I can view the stop watch and cycle counter?
Never used it myself with JTAG but the simulator can do it, may be possible with the JTAG too. I'll check later on today when I start working with Studio.
Quote:
6 Mhz external crystal on my target board would that be a Med or high frequency in the fuse setting?
Medium frequency up to 8MHz.

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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Just checked with the JTAG Mk2 and neither the stop watch or the cycle counter are updated in JTAG mode.

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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That is what was going on for me too. My timer compare works i the simulator fine. I'm going to try with my logic analyzer.
Thanks
John

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Frisky wrote:
is it possible to set the crystal frequency so I can view the stop watch and cycle counter?

A hint:
https://www.avrfreaks.net/index.p...

No RSTDISBL, no fun!