1.6.1. Treat the TCK Signal Trace as a Clock Tree
The TCK signal is the clock for the entire JTAG chain of devices. Because these devices are edge-triggered by the TCK signal, you must protect the TCK signal from high-frequency noise and ensure that the signal integrity is good.
Ensure that the TCK signal meets the rise time (tR) and fall time (tF) parameters specified in the data sheet of the relevant device family.
You may also need to terminate the signal to prevent overshoot, undershoot, or ringing. This step is often overlooked because the signal is software-generated and originated at a processor general-purpose I/O pin.
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