On Thu, 2011-03-24 at 14:34 +0000, Michael Watterson wrote:
> On 24/03/2011 14:11, Herbert Graf wrote:
> > Think of JTAG as a physically compatible interface between parts (you
> > can place dissimilar parts on the same JTAG chain, most of the time),
> > nothing more.
> >
> > While there are some "JTAG protocol" standards out there (mostly for
> > very simple stuff like reading some ID), most parts require way more
> > then what the standards iron out.
> >
> > Beyond that, there is no universal "JTAG dongle" for connecting a JTAG
> > port to a PC. Every manu has their own dongle designed to work with
> > their own software.
>=20
> It's basically a chained shift register.
> Data in
> Data out
> Clock
> maybe Reset and a few such control pins

Yes, the problem though is most commercial software out there to access
a device over JTAG expects to be communicating with it's own manus
dongle, hence my statement that there is no "universal" JTAG dongle.

If OTOH you are outside of the commercial space (using home brew/open
source/community driven software) then there are many more options. That
said, some commercial options DO support "simple" JTAG dongles, Altera
did/does for some of it's parts.=20

TTYL

--=20
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