SimCom SIM800 Hardware Design page 23

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VBAT
100K
Power on/off
PWRKEY
logic
1K
4.7K
Turn on/off
impulse
Module
47K
Figure 10: Power on/off module using transistor
VBAT
100K
Power on/off
PWRKEY
logic
1K
Module
Figure 11: Power on/off module using button
The power on timing is illustrated as following figure.
T>1.4s
VBAT
T>1.2s
V <0.7V
PWRKEY
IL
(INPUT)
T=100ms
VDD_EXT
t>3s
STATUS
Serial Port
Active
Undefind
Figure 12: Timing of power on module
When power on procedure is completed, SIM800 will send following URC to indicate that the module is ready to
operate at fixed baud rate.
RDY
This URC does not appear when autobauding function is active.
Note: User can use AT command "AT+IPR=x" to set a fixed baud rate and save the configuration to
non-volatile flash memory. After the configuration is saved as fixed baud rate, the Code "RDY" should be
received from the serial port every time when SIM800 is powered on. For details, please refer to the chapter
"AT+IPR" in document [1].
SIM800_Hardware Design_V1.10 23 2018-08-13