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
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,
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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