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M20 Hardware Design
GPRS IDLE
GPRS
STANDBY
GPRS
READY
GPRS DATA
POWER DOWN
Normal shutdown by sending the "AT+QPOWD=1" command, or by using the
pin PWRKEY or using the pin EMERG_OFF
band part of the module will be turned off, and only the power supply for the
RTC is remained. The serial interfaces are not accessible.
Minimum
The "AT+CFUN=0" command can be used to set the module to the minimum
functionality
functionality mode without removing the power supply. In this mode, both the
mode
RF part and SIM card are closed while the serial interface is still accessible. If
the slow clocking mode is enabled by "AT+QSCLK=1", the power consumption
would be less than 0.9mA.
Alarm mode
RTC alert function wakes up the module from POWER DOWN mode. The
module doesn't attempt to register to GSM network and only part of AT
commands can be available. The module would return to POWER DOWN mode
if failing to issuing "AT+CFUN=1" within 90 seconds after wakeup.
①Use the pin EMERG_OFF only when it fails to turn off the module by the "AT+QPOWD=1"
and the pin PWRKEY. Please refer to Chapter 3.4.2.4.
3.3 Power supply
The power supply of the module is from a single voltage source of VBAT= 3.4V...4.5V. The
GSM transmitting burst can cause obvious voltage drop at the supply voltage thus the power
supply must be carefully designed and is capable of providing sufficient current up to 2A. For the
VBAT input, a bypass capacitor of about 100 µF with low ESR is recommended. Multi-layer
ceramic chip (MLCC) capacitor can provide the best combination of low ESR and small size but
may not be economical. A lower cost choice could be a 100 µF tantalum capacitor with low ESR.
A small (0.1µF to 1µF) ceramic capacitor should be in parallel with the 100µF capacitor, which is
illustrated in Figure 2. The capacitors should be placed as close as possible to the M20 VBAT
pins.
M20_HD_V1.01
The module has not registered to GPRS network. The module
is not reachable through GPRS channel.
The module has registered to GPRS network, but PDP context
is inactive. The SGSN knows the Routing Area where the
module is located in.
The PDP context is active, but no data transfer is going on. The
module is ready to receive or send GPRS data. The SGSN
knows the cell where the module is located in.
There is GPRS data in transfer. In this case, power
consumption is related with network settings (PCL, GPRS
multi-slot configuration).
. The power supply to the base
①
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