GTA04 ... JTAG

Joerg Reisenweber joerg at
Tue Apr 29 21:11:21 CEST 2008

Andy Green schrieb:
> |>> Well we can make a debug connector how we like for the prototype,
> |
> | That's what it's all abut if I got this right: the prototype, to test
> | the 'new' JTAG circuitry and have a fallback option.
> | I suggested a 4pin mini-jumper thing for this purpose. You could jumper
> | it to chain 6400 and 430, and you could access each of them with an
> | individual debug board, as proposed by Allen.
> | BTW: mustn't forget to have separate clock and rst then as well. :-o
> The FTDI circuit should be low risk since we copy it from old Debug
> board schematics.  I will try to propose a little mux action controlled
> from FTDI IO to allow clean access to MSP430 UART for programming it
> also from FTDI chip.

Please, before we start to mux UARTs again, and get real bad headache
like on GTA01 that lasts until last GTA04 ceases to exist, and even
beyond (coredesign!!!) - could we line up a MSP430 EvalBoard and some
S3C-CPU (e.g. a GTA02 board) and daisychain their JTAG lines to a
debugboard to **TEST** whether we need to do such nasty hacks. JTAG is
designed _exactly_ to be chained up like this, no risk at all in hw,
patching software should be an afternoon's work (if needed at all), and
mux (WAAAHH) probably -no most likely- will introduce *more* *risk* to
GTA04 prototype hw & sw development than chaining up a whole fab of JTAG

Also see: ''Re: [gta02] GTA04 fast prototype list (base on GTA02 form


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