[J-core] Seeking help with SH7750 JTAG

[Francisco Javier Bizcocho Antúnez]

Maybe, somebody knowns some person involved with the SH4 CPU?. It just
blows my mind how it's possible that this H-UDI subsystem is still top
secret after 20 years, and literally it's impossible to get proper
documentation.

On 8 January 2018 at 06:59, Rob Landley <rob at landley.net> wrote:

> On 01/05/2018 02:04 PM, Francisco Javier Bizcocho Antúnez wrote:
> > Hello all,
> > I'm aware that this might not be ideal forum for this question, but
> > hopefully somebody knows something about this.
> >
> > Long story short, I'm trying to hook up a JTAG to a retail Dreamcast
> > (SH7750 as you might know), but regardless what I do, it looks like the
> > JTAG won't establish a connection succesfully.
> >
> > I have two different probes, an old CodeScape probe, and a new one
> > called XrossFinder, and both fail to connect through H-UDI.
> >
> > I manage to gather some of this super secret H-UDI information and they
> > refer to something called SH4-EV. I'm hopping that this means, just
> > changing some signal so it will start the H-UDI subsystem (like we could
> > see in SH3).
> >
> > Any ideas?, I hope that the retail Dreamcast is not carrying a variation
> > of SH4 that doesn't support JTAG, but rather it has been "disabled"
> somehow.
> >
> > Thank you very much in advance.
>
> Not really my area, but I found
>
> https://assemblergames.com/threads/sega-dreamcast-system-
> ram-16mb-jtag-hack.41785/
>
> Rob
>
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