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L816-AM Hardware User Manual
Page 30 of 42
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 SIM1_CLK and SIM1_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.
3.6
GPIO
The L816-AM module provides four signals to indicate the operating status of the module, the status
indicator pins are as follows:
Pin
Pin Name
I/O
Reset Value Pin Description
Type
28
FW_Ready
O
PD
Modem SMS Ready Inform
HOST 1.8V
CMOS 1.8V
29
SMS_Ready
O
PD
Modem FW Ready Inform
HOST 1.8V
CMOS 1.8V
30
USB_En/Disable
O
PD
Reserved
CMOS 1.8V
39
Wakeup_Host
O
PD
Module wakes up Host (AP).
CMOS 1.8V
33
PA_Blanking
O
PD
PA Blanking output, external
GPS control signal.
CMOS 1.8V
42
GPIO_Modem
O
PD
Reserved
CMOS 1.8V
