[openwince-list] The meaning of the JTAG TRST pin?

[Jeff C. <jc...@li...>]

I've recently tried an experiement using a PowerPC board with a JTAG
port and a Xilinx JTAG cable.

The Xilinx cable has 6 pins: GND, VCC, TMS, TDI, TDO and TCK. It works
with the linux jtag command as a DCL5 cable. and I can correctly
identify the Xilinux chips on my board.

The thing I never realized is that JTAG ports also have a TRST pin; but
I don't even have this pin on my cable! I guess the Xilinx parts are
smart, they don't need you to assert this point for the part to be
programmed.

But, my powerpc board does have a TRST pin on it's jtag port. I tried to
hook up my DLC5 cable and hoped I could identify the powerpc chip. I
would have been happy to see that work! Alas, it didn't. I wonder what
the TRST pin does then?

Anyone have a cable they would recommend using that has a TRST pin?

Jeff