C3.6. Summary Of State Transitions; Rtc Backup - Quectel M12 Hardware Design

M12 Hardware Design

Receive a voice or data call from network to wake up module.

Receive a SMS from network to wake up module.
Note: DTR pin should be held low level during communicating between the module and DTE.

c3.6. Summary of state transitions

Table 7: Summary of state transition
Current mode
Power down
Power down
"AT+QPOWD", use
Normal mode
PWRKEY pin, or use
EMERG_OFF pin
Sleep mode Use PWRKEY pin, or
use EMERG_OFF pin

3.7. RTC backup

The RTC (Real Time Clock) can be supplied by an external capacitor or battery (rechargeable or
non-chargeable) through the pin VRTC. A 1.5K resistor has been integrated in the module for
current limiting. A coin-cell battery or a super-cap can be used to backup power supply for RTC.
The following figures show various sample circuits for RTC backup.
Non-chargeable
Backup Battery
Figure 14: RTC supply from non-chargeable battery
M12_Hardware_Design_V3.3
Next mode
Normal mode
Use PWRKEY
Pull DTR down or
incoming call or SMS
or GPRS data
transmission
1.5K
VRTC
Sleep mode
Use AT command
"AT+QSCLK=1" and
pull DTR up
Module
RTC Core
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