Wake Up Sim900-Ds From Sleep Mode 2 (At+Csclk=2); Rtc Backup - SIM Tech SIMCom SIM900-DS Hardware Design

4.3.5

Wake Up SIM900-DS from Sleep Mode 2 (AT+CSCLK=2)

When SIM900-DS is in sleep mode 2 (AT+CSCLK=2), the following methods can wake up the module:
Send data to SIM900-DS via serial port.
Receive a voice or data call from network.
Receive a SMS from network.
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Note: The first byte of the user's data will not be recognized.
4.4

RTC Backup

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
Non-chargeable battery backup
Rechargeable battery backup
SIM900-DS_Hardware Design_V1.00
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Figure 14: RTC supply from capacitor
Figure 15: RTC supply from non-chargeable battery
Figure 16: RTC supply from rechargeable battery
Smart Machine Smart Decision
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2013-01-20