User's Manual
Table Of Contents

H350 LGA Serials Module Hardware User Manual Page of
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The layout signals of the SIM card should be away from any possible EMI interference sources, such
as the RF antenna and digital switching signals.
To ensure signal integrity, the length between SIM interface signals and module should not exceed
100 mm
To avoid crosstalk between USIM_CLK and USIM_IO, it is recommended to route them separately on
the application board, and preferably isolated by a surrounding ground plane.
The SIM card signals should be protected from ESD using very low capacitance protective elements
(like Zener diode). The recommended part no of ESD is AVR-M1005C080MTAAB (TDK). ESD
component should layout with SIM hold closely.
5.6.4 USIM Hot Plug
H350 supports SIM hot plug.
5.6.4.1 Hardware Connection
SIM hot plug function interacts with USIM_CD signal.
When no SIM card, USIM_CD is low level; insert SIM, USIM_CD is high level.
Explanation:
For normally closed SIM card circuit, as shown in Figure 5-8, USIM_CD connects Pin8 (SW2) of U2, Pin7
(SW1) connects GND. When there is no SIM card, SW2 and SW1 are shorted, so, SW2 is low level, when
insetting SIM card, SW1 and SW2 are disconnected, USIM_CD is pulled up.
For normally open SIM card circuit, as shown in Figure 5-9, USIM_CD connects Pin8 (SW2) of U2, and it
also connects GND with 47K resistor, Pin 7 is pulled up with 47K resistor. When no SIM card, SW2 and
SW1 are disconnected, so SW2 is low level, after inserting SIM, SW2 and SW1 are shorted, USIM_CD is
pulled up.
5.6.4.2 Software Configuration
“+MSMPD” AT command defines the SIM card status detection feature.
When set AT+MSMPD=0, the SIM detected feature deactivated. Module does not detect USIM_CD
signal.
When set AT+MSMPD=1, the SIM detected feature activated. USIM_CD pin can test whether SIM card is
onsite or not.
SIM_CD is High level, SIM card is onsite, and module registers the network automatically.
SIM_CD is Low level or not connected, SIM card is offsite and module drops out the network.
Note: The +MSMPD default value is “1”. USIM_CD is only used for SIM card hot plug detecting,
Module won’t detect SIM_CD at the first starting (it means the module will read SIM card data and register
network at the first time starting, no matter pin SIM_CD is high level or low level).