SIM900D Hardware Design
3.7 Power Saving
There are two methods for the module to enter into low current consumption status. “AT+CFUN” is used to set
module into minimum functionality mode and DTR hardware interface signal can be used to lead system to be in
SLEEP mode (or slow clocking mode).
3.7.1 Minimum Functionality Mode
Minimum functionality mode reduces the functionality of the module to a minimum and, thus, minimizes the
current consumption to the lowest level. This mode is set with the “AT+CFUN” command which provides the
choice of the functionality levels <fun>=0
，
1
，
4
z
0: minimum functionality;
z
1: full functionality (default);
z
4: disable phone both transmit and receive RF circuits;
Table10: The Current consumption of different configuration of AT+CFUN
MODE
SLEEP
AT+CFUN
1
4
0
Current Consumption
1.306mA
0.967mA
0.897mA
If SIM900D has been set to minimum functionality by “AT+CFUN=0”, the RF function and SIM card function
will be closed. In this case, the serial port is still accessible, but all AT commands correlative with RF function or
SIM card function will not be accessible.
If SIM900D has been set by “AT+CFUN=4”, the RF function will be closed, the serial port is still active. In this
case all AT commands correlative with RF function will not be accessible.
After SIM900D has been set by “AT+CFUN=0” or “AT+CFUN=4”, it can return to full functionality by
“AT+CFUN=1”.
For detailed information about “AT+CFUN”, please refer to
related document [1].
3.7.2 Sleep Mode I (CSCLK=1)
User can control SIM900D module to enter or exit the SLEEP mode (CSCLK=1) in customer applications
through DTR signal.
When DTR is in high level
，
and there is no data on air and hardware interrupt (such as GPIO interrupt or data in
serial port), SIM900D will enter SLEEP mode automatically. In this mode, SIM900D can still receive paging or
SMS from network but the serial port is not accessible.
Note: For SIM900D, it requests to set AT command “AT+CSCLK=1” to enable the sleep mode. The default
value is 0, which can not make the module enter SLEEP mode. For more details please refer to related
document [1].
SIM900D_Hardware Design_V1.04
2010.10.09
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