ARM Jtag interface vs GDB

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I was thinking about making an ethernet to JTAG interface for debugging ARM
systems. The hardwars will not be too difficult, but I was wondering is
there are any open protocols to for example to debugging via gdb over
ethernet->jtag.  The pricing of readily available interfaces is above budget
:-(

Any info or experience somewhere related to jtag debugging ?


Marcel



Re: ARM Jtag interface vs GDB
Sometimes a stub is written to talk to the JTAG interface and also interface
to GDB.  AVARICE is an example of this for the AVR JTAG Emulator.

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ARM
budget



Re: ARM Jtag interface vs GDB

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ARM
budget

The GDB remote protocol is documented in the GDB manual.

It can be sent over a serial line or TCP connection. If you have an
Ethernet/TCP/IP protocol stack, you can run the standard GDB protocol there.

A different story is the JTAG protocol - it is different for each processor.
The ARM7TDMI protocol is described in the ARM processor documentation.

HTH

Tauno Voipio
tauno voipio @ iki fi




Re: ARM Jtag interface vs GDB
What is usual for the so called GDB enabled JTAG debugger boxes is that they
have a firmware with GDB stub i.e. they know how to speak with GDB using
open remote protocol. On the other side they know how to talk to a
particular CPU using EJTAG. Thus, you can exploit the power of JTAG using
GDB. This means further that because JTAG box is in control of the external
CPU using JTAG you may debug the terget even if the target crashes (not the
case when the GDB stub is embedded in the target's firmware).

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there.
processor.



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