TCLK when TAP controller disable

Question: To disable the TAP controller, TCK must be tied LOW (VSS) to prevent clocking of the device. If tie high is the same, pull up, just not leave it float.

 

Answer:

There are no internal pull downs for the TCK. The pin can be left floating; however we do not recommend it. TCK can be tied high; however, it is not a usual practice. Our recommendation would be to tie TCK low for disabling the JTAG. This is a recommendation as per IEEE specifications.