Reproduction forbidden without Fibocom Wireless Inc. written authorization - All Rights Reserved.
FM350-GL Hardware Guide
Page 31 of 59
Figure 3-17 Reference circuit for N.O. SIM card slot
The principles of the N.O.SIM card slot are described as follows:
When the SIM card is detached, it connects an open circuit between CD and SW pins, and drives
the SIM_DETECT pin low.
When the SIM card is inserted, it connects the short circuit between CD and SW pins, and drives the
SIM_DETECT pin high.
USIM Hot-Plug
The FM350 module supports the SIM card hot-plugging function, which determines whether the SIM card
is inserted or detached by detecting the SIM_DETECT pin state of the SIM card slot.
The SIM card hot-plugging function can be configured by “AT+MSMPD” command, and the description for
AT command as shown in the following table:
AT Command
Hot-plugging
Detection
Function Description
AT+MSMPD=1 Enable
Default value, the SIM card hot-plugging detection function is
enabled.
The module can detect whether the SIM card is inserted or not
through the SIM_DETECT pin state.
AT+MSMPD=0 Disable
The SIM card hot-plugging detect function is disabled.
The module reads the SIM card when starting up, and the
SIM_DETECT status will not be detected.
Note:
SIM_DETECT is active high, it can be swapped to active low by AT CMD.
USIM Design
The SIM card circuit design should 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