[sdiy] Freescale Soundbuite

[Eric Brombaugh]

ASSI wrote:
> On Dienstag 05 Februar 2008, Rainer Buchty wrote:
>> Even worse, the 3A board requires a dedicated programming cable
>> whereas the 3E board comes with on-board USB.
> 
> But the common $20 JTAG cables do work or not?

Depends on which $20 JTAG cable you're talking about. They're not all 
created equal because every mfg/mkt-segment has their own idea of what 
should be standard. For example:

* Most ARM processor-based boards use a common 20-pin 0.1" 2x10 header, 
but it often needs a clock feedback pin for high-speed debug. 
Determining if your board needs this is 'interesting'. Then there's ST 
Semiconductor, who can't use ARM standard pinouts even for their ARM 
products...

* Xilinx uses a 14-pin 2mm 2x7 header on _some_ of their boards. The 
S3Esk doesn't have this though and uses a direct USB interface. There 
are fly-wire adaptors available to go from the 2mm connectors to 
anything you've got.

* Digilent provides a 6-pin 0.1" 1x6 header for their JTAG-capable boards.

ad-infinitum...

Then there's the driver software. Serial? Parallel-port? USB? Which pins 
of the serial/parallel port map to which JTAG signals? Is the software 
driving the bus 'intelligently', or just playing a pre-packaged SVF 
file? If the latter, operational reliability is seriously reduced 
because programming can fail silently and you'll never know until after 
you're done.

The nice things about standards are that there are so many to choose from.

FWIW, I've got some of each of the above JTAG interfaces. The only ones 
that work reliably on Xilinx boards & parts are the Xilinx-provided 
ones. YMMV.

Eric