Ri Behaviors - SimCom SIM800 Hardware Design

Module(DCE)
UART1_TXD
UART1_RXD
The serial port supports the CMOS level. If user connects the module to the computer, the level shifter should be
added between the DCE and DTE.

4.6. RI Behaviors

Table 11: RI Behaviors
State RI response
Standby High
The pin is changed to low. When any of the following events occur, the pin will be
changed to high:
Voice call
(1)Establish the call
(2)Hang up the call
The pin is changed to low. When any of the following events occur, the pin will be
changed to high:
Data call
(1)Establish the call
(2)Hang up the call
The pin is changed to low, and kept low for 120ms when a SMS is received. Then it is
SMS
changed to high.
The pin is changed to low, and kept low for 120ms when some URCs are reported. Then it
URC
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
SIM800_Hardware Design_V1.10
Serial Port
GND
PWRKEY
Figure 25: Connection for software upgrading
RI
Idle
Figure 26: RI behaviour of voice calling as a receiver
33
Smart Machine Smart Decision
I/O Connector
TXD
RXD
GND
PWRKEY
Establish the call
Hang up the call
Ring
2018-08-13