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Is there any compatibility difference between The parallel JTAG PC4 and JTAG III??

Started by jack lalo February 22, 2005
Hi all,
  I'm asking if there is any difference between the Xilinx JTAG III
and IV??? I saw that the speed of the second is 8 time quicker than
the first, but i need a JTAG cable and all the schematics are for the
old one. Is it matter if i use the JTAG III instead of the PC4???
  thanks
"jack lalo" <jacklalo020@hotmail.com> schrieb im Newsbeitrag
news:a8960e4e.0502221344.36b6aec6@posting.google.com...
> Hi all, > I'm asking if there is any difference between the Xilinx JTAG III > and IV??? I saw that the speed of the second is 8 time quicker than > the first, but i need a JTAG cable and all the schematics are for the > old one. Is it matter if i use the JTAG III instead of the PC4??? > thanks
The good old one is just a tristate buffer. Can be easy rebuild. But you should add a RC-filter and two schmitt triggers in from of the TCK/CCLK line, since the signal from the parallel port might by noisy. Another point is, that the PC-III is only recommended with IO voltages of 5/3.3V. 2.5 might work or not. PC-IV works down to 1.5, AFAIK. And its faster, since it uses (years too late) ECP mode to transfer 8 bit of data and serialize them on the POD. Some yaers ago I did my own download cable design, using a 32 macrocell coolrunner and own control software. Downloading was at an instant. BING!! Why the hell has noone already done something like this and sells them? Especially for the big Virtex-II'n stuff life would be so much easier. Regards Falk P.S. I can email you the modified schematics of the PC-III if you like. Drop me a mail.