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I am designing a circuit using the EFM32ZG222 MCU (an ARM Cortex M0+) and I need to use the SWD interface (with a 10-pin Cortex Debug Connector) along with a reset button. I found a schematic that shows typical connections for the SWD interface:

Typical SWD Connections

The problem is that the pin named "RESETn" on the MCU is to be used both by the debug interface and a reset button. I am not sure that the debug interface can handle the discharge current from the 100 nF capacitor (see the schematic below).

Reset button and debug connector

I would like to know how use both a reset button and the debug interface at the same time.

Thanks in advance :-)

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Discharge energy of a 100nF capacitor at 3.3V is roughly 550 nanoJoules. That's not a lot.

The debug interface will probably have strong drivers or an open collector that will cope with this. It has to be fairly robust in order to survive ambient electrostatic discharge while not plugged in. If that's a recommended circuit or one used by someone else then I'm sure it will be fine. If you're really worried put another one of those 22R in series with it; you can swap it later for 0R on the PCB if you want.

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Silabs provides an application note regarding the hardware design (AN0002; download AN0002SW for some reference designs). There they also use a 100nF cap on the reset pin. But according to the application note, you can drop the pullup resistor since there is one builtin (so the pin can be left floating).

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