With and without MPU block diagrams

Werner Almesberger werner at openmoko.org
Thu Apr 24 21:55:08 CEST 2008

Andy Green wrote:
> | 3. Any suggestion on FTDI chip's GPIO, I remember there are some
> | available could be used.
> The main one was reset, but we have that in there already.  Thinking
> about what I do during development, it's just really reset that I use.
> Maybe someone else can have an idea.

As far as I recall, we only have one spare GPIO, and that's the one
we use for the NOR write protection in GTA02. All the other GPIOs
are either used actively for JTAG or the serial console, or they have
some fixed role and can't be freely programmed. (Such as the ones
driving the TX/RX LEDs on the debug board.)

In case we do want to do something fancy, we could also reconfigure
the FTDI to a mode that gives us more control over the GPIOs. It won't
do JTAG and/or serial console then, though.

> The two issues we have here are 1) we only have one TAP controller
> defined in the FTDI :-) so there's trouble having two chains,

That's a very diplomatic way of saying "it doesn't really work" ;-)

> and a
> secondary issue is that I wonder if openOCD is well tested and bug free
> if the CPU isn't the first or maybe last device in the chain.

You'll probably have to extend OpenOCD. I also don't know offhand if it
supports the MSP430, let alone two CPUs in the same chain. I suppose
Milosch can clarify the former. The latter may need some hacking.

- Werner

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