Smart Machine Smart Decision
4.7
SIM Card Interface
4.7.1
SIM Card Application
SIM900-DS provides two SIM card interfaces. The interface complies with the GSM Phase 1 specification and
the new GSM Phase 2+ specification for FAST 64 kbps SIM card. Both 1.8V and 3.0V SIM card are supported.
The SIM interface is powered from an internal regulator in the module.
It is recommended to use an ESD protection component such as ST (
) ESDA6V1W5 or ON SEMI
) SMF05C.The pull up resistors (15K
Ω
) on the SIM1_DATA and SIM2_DATA line are
already added in the module internal. Note that the SIM peripheral circuit should be close to the SIM card socket.
The reference circuit of the 8-pin SIM card holder is illustrated in the following figure.
SIM900-DS_Hardware Design_V1.00
29
2013-01-20
MODULE
SMF05C
VCC GND
RST VPP
CLK I/O
PRESENCE GND
10K
22R
22R
22R
100nF
VDD_EXT
MOLEX-91228
SIM
CARD
22pF
Figure 25: Reference circuit of the 8-pin SIM card holder
The SIM_PRESENCE pin is used for detection of the SIM card hot plug in. User can select the 8-pin SIM card
holder to implement SIM card detection function. AT command “AT+CSDT” is used to enable or disable SIM
card detection function. For details of this AT command, please refer to
document [1]
.
If the SIM card detection function is not used,
user can keep the SIM_PRESENCE pin open. The reference
circuit of 6-pin SIM card holder is illustrated in the following figure.
Figure 26: Reference circuit of the 6-pin SIM card holder
