MTX-xG-JAVA-IoT Family
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MTX M2M® by MATRIX ELECTRONICA S.L.U
4.4.2 RS232 interface
The STD and DB15 models support a standard RS232 4-wire serial interface (EIA/TIA 574) via its 15 pin
Sub-D connector.
Port signals are connected to an internal coprocessor through a transceiver. In the STD model, which
has two RS232 and a RS485 port, this coprocessor selects which of those ports are connected to the
Cinterion GSM engine’s UARTs ASC0 and ASC1. Users can select the ports configuring the device’s DIP
switches. Please read section 4.7 to learn how to configure DIP switches in order to select the port of
your choice.
The MTX-IoT modem is designed to be used as a DCE (data circuit-terminating equipment). Based on
the conventions for DCE-DTE connections, it communicates with the customer application (DTE- data
terminating equipment) using the following signals:
• Port TxD @ application sends data to MTX-3G-JAVA Terminal’s TD.
• Port RxD @ application receives data from MTX-3G-JAVA Terminal’s RD.
The RS232 interface is implemented as a serial asynchronous transmitter and receiver conforming to
ITU-T V.24 Interchange Circuits DCE. It is configured for 8 data bits, no parity and 1 stop bit and can be
operated at fixed bit rates from 300bps to 460.8kbps.
The electrical characteristics of the serial port signals are shown below:
Features (when connected to ASC0 or ASC1)
• Includes data lines TD1 and RD1 (2-wire/4-wire)
• Includes the status lines RTS1 and CTS1 and supports hardware flow control (4-wire only)
• The default configuration is 8 data bits, no parity and 1 stop bit. The setting can be changed
using the AT command AT+ICF and, if required, AT^STPB.
• Can be operated at fixed bit rates from 1200 bps to 921600 bps. Autobauding is not supported.
• The default serial speed for MTX-IoT is 115200bps.
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