I've used JTAG to debug and program a couple of embedded systems. I
even had an automated regression test suite that tested some AVR
hardware using gdb running on Gentoo talking to an JTAG. Freaky but
fun.
If I recall correctly many chips will allow you to see and twiddle
internal registers and states of sub-blocks in the integrated circuits.
I never had the call to go to that level, but some have. What little I
remember is that the JTAG standard dictates the timing and pin-out on a
20 pin connector. But I also remember that the ARM and AVR JTAG units I
saw do not play together, but there might be some universal JTAG
interfaces now.
Several years ago I was told to stay clear of the USB interfaced JATGs
and to use a USB/RS232 converter hooked up to a RS232/JTAG interface as
this was more reliable. That was years ago, and things are likely more
stable now. I also remember seeing some open source hardware/software
JTAG efforts. That might make a good place to start working through the
JTAG protocal.
Hope that helps.
EBo --
On Tue, 26 Oct 2010 19:49:46 +0100, Steve Simon wrote:
I am intrigued, what facalities would jtag software provide on plan9,
is the idea a virtual filesystem which would communicate with a
fairly
dumb jtag interface connected to (say) a PC's printer parallel port,
or may there is some standardised USB interface?
I jse jtag probes from time to time but I have never thought about
the code to
implement what is on the probe...
What was discussed (roughly).
-Steve
