|Debug interface (DEBUG)|
For debugging purposes, it is useful to provide access to the ISP entry pin PIO0_1. This pin can be used to recover the part from configurations which would disable the SWD port such as improper PLL configuration, reconfiguration of SWD pins, entry into Deep power-down mode out of reset, etc. This pin can be used for other functions such as GPIO, but it should not be held LOW on power-up or reset.
The VTREF pin on the SWD connector enables the debug connector to match the target voltage.
Connecting the SWD pins to a standard SWD connector
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