1)
This pin is pulled LOW by default, and will be internally pulled up to 1.8 V by software configuration only
when (U)SIM hot-plug is enabled by AT+QSIMDET.
4.1.2. Normally Closed (U)SIM Card Connector
With a normally closed (U)SIM card connector, USIM_DET pin is shorted to ground when there is no
(U)SIM card inserted. (U)SIM card detection by high level is applicable to this type of connector. After
executing AT+QSIMDET=1,1 to enable the (U)SIM hot-plug: when a (U)SIM card is inserted, USIM_DET
will change from low to high level; when the (U)SIM card is removed, USIM_DET will change from high to
low level.
⚫ When the (U)SIM is absent, CD is shorted to ground and USIM_DET is at low level.
⚫ When the (U)SIM is present, CD is open from ground and USIM_DET is at high level.
The following figure shows a reference design for (U)SIM interface with a normally closed (U)SIM card
connector.