SIM Tech SIMCom SIM800C - Page 30

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SIM800C_Hardware_Design_V1.00 30 2014-10-30
changed to high.
URC
The pin is changed to low, and kept low for 120ms when some URCs are reported. Then it is
changed to high. For more details, please refer to document [10].
The behavior of the RI pin is shown in the following figure when the module is used as a receiver.
HIGH
LOW
Idle Ring
Hang up the call
Establish the call
RI
Figure 25: UART1_RI behaviour of voice calling as a receiver
HIGH
LOW
Idle Ring
Hang up the call
Establish the call
RI
Figure 26: UART1_RI behaviour of data calling as a receiver
HIGH
LOW
Idle
RI
120ms
Receive SMS
URC
Figure 27: UART1_RI behaviour of URC or receive SMS
However, if the module is used as caller, the UART1_RI will remain high. Please refer to the following figure.
HIGH
LOW
Idle
Ring
Establish
the call
Hang up
the call
Idle
RI