From mboxrd@z Thu Jan 1 00:00:00 1970 To: <9fans@9fans.net> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Date: Tue, 26 Oct 2010 14:10:30 -0500 From: EBo In-Reply-To: <06fed67ccccb147c7e18240205ff0ca0@quintile.net> References: <06fed67ccccb147c7e18240205ff0ca0@quintile.net> Message-ID: <1b5a7cf45e8c570c416d1d08b607bb35@swcp.com> User-Agent: RoundCube Webmail/0.4-trunk Subject: Re: [9fans] JTAG Topicbox-Message-UUID: 6e2d303c-ead6-11e9-9d60-3106f5b1d025 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