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Old 02-22-2005, 10:44 PM
jack lalo
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Default Is there any compatibility difference between The parallel JTAG PC4 and JTAG III??

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
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Old 02-23-2005, 05:36 PM
Falk Brunner
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Default Re: Is there any compatibility difference between The parallel JTAG PC4 and JTAG III??


"jack lalo" <[email protected]> schrieb im Newsbeitrag
news:[email protected] om...
> 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.



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