SIM340 Hardware Design
VDD_EXT
（
OUTPUT
）
V
IL
<0.2*VBAT
V
IH
> 0.6*VBAT
Pulldown > 2s
Hiz
VBAT
PWRKEY
(INPUT)
Figure 9: Timing of turn on system
When power on procedure complete, the SIM340 will send out following result code to indicate
the module is ready to operate when set as fixed baud rate.
RDY
This result code does not appear when autobauding is active.
3.4.3 Turn on SIM340 using the RTC (Alarm mode)
Alarm mode is a power-on approach by using the RTC. The alert function of RTC makes the
SIM340 wake up while the module is power off. In alarm mode, SIM340 will not register to GSM
network and the software protocol stack is closed. Thus the parts of AT commands related with
SIM card and Protocol stack will not be accessible, and the others can be used as well as in normal
mode.
Use the AT+CALARM command to set the alarm time. The RTC remains the alarm time if
SIM340 is power down by “AT+CPOWD=1” or by PWRKEY pin. Once the alarm time is expired
and executed, SIM340 will go into the alarm mode. In this case, SIM340 will send out an
Unsolicited Result Code (URC) when set as fixed baud rate:
RDY
ALARM
MODE
This result code does not appear when autobauding is active.
During alarm mode, use AT+CFUN command to query the status of software protocol stack; it
SIM340_HD_V3.09
18.03.2009
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