Hi All, I'm building a JTAG chain demultiplexer so I can control 30 identical JTAG chains from a single point. Can anyone confirm the quiescent (not doing anything) states of the JTAG pins; so I know what to hold the pin levels at when a chain is not being used. I see that TMS, TCK & TDI have internal pull-ups, so would I place a logical 1 on these when they're not in use? TDO is easy enough to sort out as it just goes high Z.
Many Thanks Andy
-- Andrew Greensted Department of Electronics Bio-Inspired Engineering University of York, UK Tel: +44(0)1904 432379 Mailto: ajg112@ohm.york.ac.uk Fax: +44(0)1904 433224 Web: www.bioinspired.com
Just for anyone who searches in the future. It seems that TDI and TMS are usually pulled high within target devices, however externally pulling them high (4.7k) is probably a good idea. TCK and TDO can be left floating.
This may help: http://support.xil> Hi All,
-- Andrew Greensted Department of Electronics Bio-Inspired Engineering University of York, UK Tel: +44(0)1904 432379 Mailto: ajg112@ohm.york.ac.uk Fax: +44(0)1904 433224 Web: www.bioinspired.com
Making sure TMS stays high is a good idea, because them any glitches on TCK will just keep (or get) the TAP controller in reset state
-Lasse
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