UNICORECOMM UM220-IV M0, Руководство пользователя

Страница: 6 / 7

3
3. Attachment
Here are two options to avoid module startup abnormality caused by string power.
Option 1

No external pull-up resistor is allowed to connect with the output pin TXD
；
Option 2

When the module is not powered on, make sure the IO port connected to the
module is in high resistance state or low level to avoid string power.