SIM Tech SIMCom SIM900-DS, Проектирование аппаратного обеспечения

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Smart Machine Smart Decision
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:
z Send data to SIM900-DS via serial port.
*
z
Receive a voice or data call from network.
z Receive a SMS from network.
*
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.
z
External capacitor backup
Figure 14: RTC supply from capacitor
z
Non-chargeable battery backup
Figure 15: RTC supply from non-chargeable battery
z
Rechargeable battery backup
Figure 16: RTC supply from rechargeable battery
SIM900-DS_Hardware Design_V1.00
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2013-01-20