CLM920_RC3(RV3 RE3)LCC Series CAT1 Module Hardware Manual
Shanghai YUGE Information Technology Co., Ltd.
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The peripheral circuit devices of the USIM interface should be placed close to the card
holder, and the SIM card holder should be close to the module layout.
The circuit of the USIM card is susceptible to radio frequency interference, which may
cause the card not to be recognized or dropped. Therefore, the card slot should be placed
as far away as possible from the antenna's radio frequency radiation, and the card wiring
should be kept away from the radio frequency, power supply, and high-speed signal line.
USIM_PRESENCE is the detection pin inserted or not inserted into the USIM card. By
default, it is high level. This pin can be used to detect the status of the SIM card during
hot plug application.
In order to avoid instantaneous voltage overload at the USIM interface, a 22R resistor
should be connected in series on the signal line path.
The ground of the USIM card holder and the module must maintain good connectivity.
3.7.2 USIM_ PRESENCE Hot Swap Reference Design
The CLM920_RC3 module supports the hot swap function of the USIM card. The
USIM_PRESENCE pin is used as an input detection pin to judge whether the USIM card is
inserted or not. The USIM_PRESENCE pin is pulled high by default. You can use AT +
HOSCFG to turn on or off the hot-swap function, which is turned off by default (see AT
command set for details).
Table 3-16 Definition of SIM card hot swap detection pins
NO AT command
USIM_PRESENCE status
Functional description
1
AT+HOSCFG=1,1 high
SIM card is inserted, the
detection pin is high
2
AT+HOSCFG=1,0 low
SIM card is inserted, the
detection pin is low
