SIM800C datasheet(23/52 Pages) SIMCOM

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SIM800C_Hardware_Design_V1.02

2015-4-27

4.3.3.

Wake Up SIM800C from Sleep Mode 1

When SIM800C is in sleep mode 1(AT+CSCLK=1), the following methods can wake up the module:



Pull down DTR pin.

The serial port will be active after DTR pin is pulled to low level for about 50ms.



Receive a voice or data call from network.



Receive a SMS from network.



Receive external interrupt.

Note: After module has received incoming call or new SMS, serial port can report URC, but the serial port can

not input AT command. Only after the DTR pin is pulled to low level for 50ms, the serial port can input AT

command.

4.3.4.

Sleep Mode 2 (AT+CSCLK=2)

In this mode, SIM800C will continuously monitor the serial port data signal. When there is no data transfer over 5

seconds on the RXD signal and there is no on air and hardware interrupts (such as GPIO interrupt), SIM800C will

enter sleep mode 2 automatically. In this mode, SIM800C can still receive paging or SMS from network.

4.3.5.

Wake Up SIM800C from Sleep Mode 2

When SIM800C is in sleep mode 2 (AT+CSCLK=2), the following methods can wake up the module:



Send data to SIM800C via main serial port (the first character will lose).



Receive a voice or data call from network.



Receive a SMS from network.

Note: Autobauding is default. It cannot enter sleep mode in the absence of synchronous serial port baud rate

after module power on.

4.4. Power Saving Mode

Current input for RTC when the VBAT is not supplied for the system. Current output for backup battery when

the VBAT power supply is in present and the backup battery is in low voltage state. The RTC power supply of

module can be provided by an external capacitor or a battery (non-chargeable or rechargeable) through the VRTC.

The following figures show various reference circuits for RTC back up.



External capacitor backup

RT C

Core

1.5K

M odule

VR T C

Large-capacitance

C apacitor

Figure 15: RTC supply from capacitor



Non-chargeable battery backup

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