User's Manual

Smart Machine Smart Decision
SIM868_Hardware_Design_V1.00 26 2016-06-20
command.
4.3.4. Sleep Mode 2 (AT+CSCLK=2)
In this mode, SIM868 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), SIM868 will
enter sleep mode 2 automatically. In this mode, SIM868 can still receive paging or SMS from network.
4.3.5. Wake Up SIM868 from Sleep Mode 2
When SIM868 is in sleep mode 2 (AT+CSCLK=2), the following methods can wake up the module:
 Send data to SIM868 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 GNSS RTC when the GPS_VBAT is not supplied for the GNSS power system. Current output
for backup battery when the GPS_VBAT power supply is in present and the backup battery is in low voltage
state. The RTC power supply of GNSS 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
Figure 15: RTC supply from capacitor
 Non-chargeable battery backup
Figure 16: RTC supply from non-chargeable battery