> 3.6 | RS-232 Interface

> The serial interface of the TC65 Terminal is intended for the communication between the GSM module and the host application. This RS-232 interface is a data and control interface for transmitting data, AT commands and providing multiplexed channels. EMC immunity complies with the vehicular environment requirements according to EN 301 489-7.
> Figure 6: Pin assignment RS-232 (D-Sub 9-pole female)

> Table 10: | 9-pole D-Sub (female) RS-232

> Pin no. | Signal name | I/O | Function of application
> 1 | DCD | O | Data Carrier Detected
> 2 | RXD | O | Receive Data
> 3 | TXD | I | Transmit Data
> 4 | DTR | I | Data Terminal Ready Attention: Low-to-high transition of the DTR line activates the ignition signal of the GSM module
> 5 | GND | - | Ground
> 6 | DSR | O | Data Set Ready
> 7 | RTS | I | Request To Send
> 8 | CTS | O | Clear To Send
> 9 | RING | O | Ring Indication

> TC65 Terminal is designed for use as a DCE. Based on the conventions for DCE-DTE connections it communicates with the customer application (DTE) using the following signals:

> • | Port TxD @ application sends data to TXD of TC65 Terminal

> • | Port RxD @ application receives data from RXD of TC65 Terminal

> Figure 7: Serial interface
> The RS-232 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 460,800bps. Autobauding supports bit rates from 1,2bps to 460,800bps. Hardware handshake using the /RTS and /CTS signals and XON/XOFF software flow control are supported.
> In addition the modem control signals DTR, DSR, DCD and RING are available. The modem control signal RING (Ring Indication) can be used to indicate, to the cellular device application, that a call or Unsolicited Result Code (URC) is received.