Hardware+Design V1.07

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reporting, then “RI” will change to low logic level to inform the master (client PC). It will stay low until
the master clears the interrupt event with AT command.
Figure 20: RI behaviour in NULL Modem
If Full Modem is used to establish communication between devices, the pin “RI” is another operation
status. Initially it keeps high, when a voice call or CSD call comes, the pin “RI” will change to low for
about 5900ms, then it will return to high level for 100ms. It will repeat this procedure until this call is
answered or hung up.
Figure 21: RI behaviour in FULL Modem
To comply with RS-232 protocol, the RS-232 level shifter chip should be used to connect SIM5320 to the
RS-232-C interface. In this connection, the TTL level and RS-232 level are converted mutually. SIMCom
recommends that user uses the SP3238ECA chip with a full modem. For more information please refers to
the RS-232 chip datasheet.
Note: SIM5320 supports the communication rate: 300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200,
230400, 460800, 921600, 3200000, 3686400, 4000000bps. Default rate is 115200bps.
3.4 Audio Interfaces
SIM5320 provides two analog signal outputs and one analog input. MIC1P/N is used as microphone,
EAR1P/N and SPK_P/N are used as audio output. Regarding audio parameters configuration, please refer
SIM5320_Hardware Design_V1.07 2012-09-21
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