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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 20:26:32 +0200
User-agent: Mutt/

On Sat, Oct 05, 2002 at 06:49:10PM +0200, Torsten Mohr wrote:
> Hi,
> great!  I also wrote some JTAG software for the parallel port to
> debug my ARM7TDMI.  When i read that the ARM controllers also
> have a JTAG port but Atmel won't release its specification
> i thought about reverse engineering it.

Maybe we can bundle some things ...

> Building some hardware that implements a JTAG TAP controller
> could help.  This hardware would get the JTAG signals TMS, TDI,
> TCK, TRST and would behave like a JTAG controller.

This is my idea too !

> This way, the speed of the JTAG-ICE shouldn't be a problem.
> Has anybody measured the speed the JTAG-ICE works with?
> What is the time period of a Clock pulse?

The clock of TCK is about 5 to 5.6 microseconds and can be a bit longer
and depends on which state the JTAG TAP machine is in. Specifically
while in DR/IR shift state it can be up to 7 microseconds (if I remember).

> This software for the parallel port i wrote runs completely in
> user space, though it depends on the /dev/parport devices of
> Linux.  It can:
> - test the parallel port (reading/writing pins with a user interface)
> - read/write several EEPROMs (24Cxx, 93X6, M95XXX) (batched or interactive)
> - read Gamepads (Playstation)
> - debug an ARM7TDMI (read/write registers/memory, download S-Records
>   and start them)
> I'll release that library under a GPL soon, at the moment i'm still
> fighting with my fresh installed Linux system.

Great I think you can do a lot of people a real BIG favour.

> Best regards,
> Torsten.
> avr-gcc-list at http://avr1.org



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