TMS, TCK, /TRST should be terminated (e.g. with 1 kOhm to Ground). The goal must be to avoid or limit reflections and cross talk between signals. Glitches and spikes on TCK most likely will cause problems during Boundary Scan.
The proper termination scheme and values will depend on test bus cable length, layout of the test bus signal traces on the PCB, any test signal buffering, the number of BScan components on the UUT, and the JTAG/Boundary Scan controller hardware, among other things.
If /TRST has a pull down resistor on the UUT, make sure to connect this signal to the Boundary Scan controller so that it can be driven to logic-high during JTAG/Boundary Scan test and ISP applications.
