Re: [Openocd-development] Need pointers getting FT2232 JTAG interface for AMD Elan SC520

[Dominic R. <Dom...@gm...>]

On Friday 25 July 2008 19:20:08 you wrote:
> I've used commercial debuggers that use the 4 JTAG signals in order to
> establish a debugging session

Have you debugged x86 targets that way? Is is possible for e.g. ARM (though 
without reset signals you're rather limited).

> and I know the ARM guys have gdbserver going 
> so I know it is possible ... I just don't know how to go about learning it.

gdbserver uses the debug functionality provided by the underlying platform, 
e.g. Linux. When talking to bare metal, you need that debug functionality in 
the hardware. For ARM (7, 9, ...), that's the EmbeddedICE macrocell.

> That is why I'm posting ... so you guys can "show me the way".
>
> Right now I would be just happy being able to flash the Soekris board I'm
> using as I would like to port a different bios to it but I would like to
> learn how to get gdb to work over the jtag link in the future.

It is possible to flash via boundary scan, but it is generally not possible to 
debug that way.

> > Debugging requires support from dedicated on-chip debug circuitry.
> > Apparently
> > the Elan SC520 has something they call "AMDebug", which probably does
> > what you want, but I'm not sure if the necessary information is publicly
> > available.
>
> AMDebug is a propritery AMD thing that I'm not interested in.

You'll probably have to look for another platform then. PowerPCs come with a 
debug interface, but there's little or no documentation to get hold off. MIPS 
support is still in an early state afaik, as Øyvind suggested it would be 
great if someone looked after the code in the MIPS branch. The Atmel 
controllers provide debug support, too, the AVR32 for example might be a nice 
target.

Regards,

Dominic