JTAG intro?
2003-12-11 by David Willmore
Hello, all. I'm new to the group as it was just pointed out to me--as well as these cute little uCs. I've done some ARM work before--I have a small collection of Webpals (CLPS7500 based-- 720 core with FPE) and I've followed ARM as a company for, hmm, decades, now, I think. These chips are cheap enough to do a lot of work that I find useful. My main hobby is amateur radio and I can see plenty of things I can do with these that a PIC just won't manage. To that end, I've been reading up on the uC and ARM development, in general. I'm getting there, but there is a lot to read through. Oh, I should compliment ARM at this point. Their web site is very well layed out (as far as the literature section goes) and didn't require anything stupid like registration or such--like Motorola or Ubicom, etc. Philips web site is okay, but a little poorly organized. I just read the DAI0028A_arm7tdmi_debug.pdf document and it looks like it should be pretty easy to debug this core. One little problem is that the document assumes some familiarity with JTAG--which I don't have. Can someone recommend a document to give me a quick understanding of JTAG? The whole scan chain idea makes complete sense, but the ARM document mentions the 16 state state machine that controls things, but does not go into detail on how that is controlled. Oh, and physical things like how fast you're allowed to clock it, etc. That's probably in the lpc data sheets, come to think of it.... So, what does everyone use for their JTAG interface? Some commercial product that's part of their development system or some quick and dirty 'latch on the parallel port' type? I was thinking that a PIC at the end of a serial cable might do a good job. Cheers, David