Atmel Atmel-ICE

When designing a target application PCB where UPDI interface will be used, the following considerations
must be made for correct operation:
• Pull-up resistors on the UPDI line must not be smaller (stronger) than 10kΩ. A pull-down resistor
should not be used, or it should be removed when using UPDI. The UPDI physical is push-pull
capable, so only a weak pull-up resistor is required to prevent false start bit triggering when the line
is idle.
• If the UPDI pin is to be used as a RESET pin, any stabilizing capacitor must be disconnected when
using UPDI, since it will interfere with correct operation of the interface
• If the UPDI pin is used as RESET or GPIO pin, all external drivers on the line must be disconnected
during programming or debugging since they may interfere with the correct operation of the
interface
Atmel Atmel-ICE [USER GUIDE]
Atmel-42330C-Atmel-ICE_User Guide-10/2016
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