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JTAG/SWI pull-up pull-down resistor

federico.massimi
Associate III

good morning, I wanted to ask a simple question.

I'm drawing the schematic of a small board based on the NUCLEO-F401RE.

I have a doubt about the JTAG/SWI connector, practically on various schemes I have seen that there are pullup/pulldown resistor (see attached) but on the NUCLEO scheme it seems to me that there are not. So the question is: do I need pull-up/pull-down on the JTAG/SWI interface?

Thanks in advance

 FM

2 REPLIES 2
Uwe Bonnes
Principal III

I general you don't need Jtag Pull Up/Down. The STM32 Jtag interface has internal pulls.

federico.massimi
Associate III

the SWD interface also have internal pull-up/down ?

in all cases do you advise me to provide pull-ups on the pcb and not to mount the resistances or is it totally useless and I do not even plan them?