After the SIM card hot-plugging detection function is enabled, the module detects that the SIM card is
inserted when the SIM_DETECT pin is high, then executes the initialization program and finish the
network registration after reading the SIM card information. When the SIM_DETECT pin is low, the
module determines that the SIM card is detached and does not read the SIM card.
Note:
By default, SIM_DETECT is active-high, which can be switched to active-low by the AT
command. Please refer to the AT Commands Manual for the AT command.
The system doesn’t need SIM hot-plug function, please left SIM_DTECT floating.
3.5.4 USIM Design
The SIM card circuit design shall meet the EMC standards and ESD requirements with the improved
capability to resist interference, to ensure that the SIM card can work stably. The following guidelines
should be noted in case of design:
The SIM card slot placement should near the module as close as possible, and away from the
RF antenna, DC/DC power supply, clock signal lines, and other strong interference sources.
The SIM card slot with a metal shielding housing can improve the anti-interference ability.
The trace length between the SIM card slot and the module should not exceed 100mm, or it
could reduce the signal quality.
The UIM_CLK and UIM_DATA signal lines should be isolated by GND to avoid crosstalk
interference. If it is difficult for the layout, the whole SIM signal lines should be wrapped with
GND as a group at least.
The filter capacitors and ESD devices for SIM card signals should be placed near to the SIM
card slot, and the ESD devices with 22~33pF capacitance should be used.
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