Hi, I have a doubt in JTAG signals.Is it necessary to add a pull up or pull down resistors for the signals TRST,TDI,TDO,TMS,TCLK in JTAG connector ?

SS.7 · ‎2018-11-10

Also in STM32 reference manual they have mentioned only about the internal pull ups and not about the external .Just want to know whether pull up or pull down resistors are required for those 5 signals?

Thanks!

Tesla DeLorean · ‎2018-11-10

Optional. You can always have pads and opt to no-fit on the BOM

You do need a pull-down on BOOT0 to ensure consistent startup, I'd recommend a pull-up on NRST, and your own reset circuit it you manage multiple supply rails.

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waclawek.jan · ‎2018-11-10

All JTAG signals are driven push-pull (i.e. all the time high or low) by the JTAG adapter, except TDO which is in turn driven by the target (STM32). The pullups are there to prevent spurious action when the adapter is not connected.

In other words, unless there's some significant noise source, the internal pullups should suffice.

JW