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Re: [avr-gcc-list] r-engineering the JTAG-ICE protocol

From: a . doesschate
Subject: Re: [avr-gcc-list] r-engineering the JTAG-ICE protocol
Date: Sat, 5 Oct 2002 17:44:40 +0200
User-agent: Mutt/

On Sat, Oct 05, 2002 at 01:23:44PM +0000, Karl Ran wrote:
> Hi there!
> I'd like to know if anyone already started to reverse-engineer the
> AVR-onchip-JTAG-ICE command-set on the newer Mega16++ AVRs.
> If not, anyone knows the complexity of the ICE command-sets on the
> microconrollers in general?


Hi Karl (and all),

I am new to this list. Hope this is ok.

Now to the JTAG interface : I am preparing an atmega16 to watch
the JTAG interface of the Atmel's Ice.

I am about to test my "watch" software of the atmega16 on the ARM7TDMI JTAG
interface which already runs succesfully under GNU/Linux (i.e. JTAG driver,
JTAG library and a simple userland testtool for the driver and library).
I was planning to release the ARM7TDMI JTAG under GPL but I had some
trouble with the synchronous character of the JTAG interface itself in
combination with an asynchronous, time slicing environment (i.e. kernel space).
The ARM7TDMI JTAG driver software itself talks to a bare bone parallel port.
If someone is interested I can explain the internals of both the ARM7TDMI
and AVR JTAG and what has to be done in kernel space (off the list of course).

My goal

When I discovered that the atmega series were running upto 16 MHz, then this
should be normally fast enough to talk to the parallel port. 
I decided to implement the JTAG protocol into the atmega16 so that 
the atmega16 itself is just an ordinary ieee1284 parallel port device. 

This has some advantages :
- theoretically you can achieve tremendous up/download speed (> 150 Kbyte/s)
- take advantage of the existing ieee1284 parallel port kernel module
- implement other synchronous debugging protocols like BDM of the
  683xx, Coldfire, PPC, HC12 series
- implement other JTAG extensions
- generalising flash programming (serial, parallel, etc)
- integrate this (debugging and programming) approach into GDB 

There is just one caveat : this device can only be tested by me on GNU/Linux
because access to the parallel port in other systems is unfamiliar to

So please be patient : things will be published in time but plenty of time isnot
what I have unfortunately (are we all ?).


* choose GNU/Linux : GNU/Linux is Freedom *


Armand ten Doesschate
Welschapsedijk 141
5652 XL Eindhoven
the Netherlands
tel : (++31) 40 2571 274
e-mail : address@hidden
avr-gcc-list at http://avr1.org

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