Research SIM 900A, Руководство пользователя

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GSM GPRS SIM900A MODEM REV1.0
POWER MODES
Power down mode
SIM900A is set power down mode by “AT+CPOWD=0”
There are two methods for the module to enter into low current consumption status
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.
If SIM900A has been set to minimum functionality by “AT+CFUN=0”
If SIM900A has been set to full functionality by “AT+CFUN=1”
If SIM900A is set “AT+CFUN=4” to disable both the above functionality.
Sleep mode
We can control SIM900A module to enter or exit the SLEEP mode in customer
applications through DTR signal. When DTR is in high level and there is no on air and hardware
interrupt (such as GPIO interrupt or data on serial port), SIM900A will enter SLEEP mode
automatically. In this mode, SIM900A can still receive paging or SMS from network but the
serial port is not accessible.
Wake up SIM900A from sleep mode

Enable DTR pin to wake up SIM900A. If DTR pin is pulled down to a low level

This signal will wake up SIM900A from power saving mode. The serial port will be
active after DTR changed to low level for about 50ms.

Receiving a voice or data call from network to wake up SIM900A.

Receiving a SMS from network to wake up SIM900A.