Wake Up Module From The Sleep Mode; Summary Of State Transition (Except Sleep Mode); Rtc Backup - Quectel M20 Hardware Design

M20 Hardware Design

3.6.3 Wake up module from the SLEEP mode

When the module is in the SLEEP mode, the following methods can wake up the module.
DTR pin
If the DTR Pin is pulled down to a low level, it would wake up the module from SLEEP
mode. The serial port will be active after about 20ms when DTR be changed to low level.
Receiving a voice or data call from network to wake up module.
Receiving a SMS from network to wake up module.
RTC alarm expired to wake up module.
Keypad and PWRKEY interrupt
Note: DTR pin should be held low level during communicating between the module and DTE.

3.7 Summary of state transition (except SLEEP mode)

Table 13: Summary of state transition
Current mode
POWER DOWN
POWER DOWN
Normal mode AT+QPOWD, use
PWRKEY pin, or
use EMERG_OFF
pin
Alarm mode Use PWRKEY
pin or wait
module turning
off automatically

3.8 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 3.9 K 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.
M20_HD_V1.01
Further mode
Normal mode Alarm mode
Use PWRKEY Turn on the module by RTC
alarm
Set alarm by "AT+QALARM",
and then turn off the module.
When the timer expires, the
module turns on automatically
and enters Alarm mode.
Use AT+CFUN
- 41 -