User's Manual Part 1

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The USIM interface is compatible with the ISO 7816-3 IC Card standard on the issues
required by the GSM 11.12 and GSM 11.18 standard.
Both 1.8 V and 3 V SIM Cards are supported.
A few comments on the SIM_DETECT signal
1. An external pull-up resistor is connected to SIM_DETECT on the WWAN M.2
module.
2. When a SIM is inserted, SIM_DETECT will be high.
3. When a SIM is removed or not present, SIM_DETECT will be low.
4. The host does not need to drive this signal. It can be tri-stated.
Table 7
(U)SIM Interface Signals
Signal Name Description
Pin
Direction
(WWAN)
Voltage
Level
UIM_CLK Clock SIM Card 32 O 1.8 V/3.0
V
UIM_DATA Input/ Output SIM Card 34 I, O 1.8 V/3.0
V
UIM_RESET Reset signal for SIM card 30 O 1.8 V/3.0
V
USIM_PWR 1.8 V/3 V Supply for SIM Card 36 O 1.8 V/3.0
V
SIM Detect SIM Card Detection 66 I 1.8 V
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The following design guidelines are recommended for the SIM card socket mounted on the
host system:
Length of the traces UIM_CLK, UIM_DATA, and UIM_RESET should not exceed
10 cm.
UIM_DATA is a sensitive open-drain bi-directional signal. It should not be mounted
beside the UIM_CLK signal for long distances. It is recommended to place the
UIM_RST trace between UIM_DATA and UIM_CLK to provide isolation. If the
traces are run a long distance, surround the UIM_DATA with ground to shield from
system noise and UIM_CLK.
The rise time for UIM_DATA should not exceed 1 µs per the 3GPP specification.
High input capacitance may increase rise time and lead to certification failure.
o Keep UIM traces with low capacitance between each other and to GND
o An ESD component with high capacitance may increase rise time.