2.5.1Serial Data

The modem supports the standard data character format of 1 start bit, 8 bit data, no parity plus 1 stop bit, in total 10 bits per character.

2.5.2Serial Data Signals - RD, TD

The default baud rate is 9.6 kbps, however higher bit rates up to 460 kbps are supported. At start-up the TT4031 (SE-GM29) transmits and receives data at the default rate of 9.6 kbps in either standard AT mode or binary mode (the first received data - AT or binary format - determines the operating mode). When reprogramming, the transmission rate is automatically negotiated by the programming application. Speeds up to 460 kbps are supported.

Serial Data From Modem (RD)

RD is an output signal that the modem uses to send data to the application.

Serial Data To Modem (TD)

TD is an input signal, used by the application to send data to the modem.

2.5.3Control Signals - RTS, CTS, DTR, DSR, DCD, RI

RTS and CTS are capable of transmitting at 1/10 th of the data transmission speed for data rates up to 460 kbps (byteoriented flow control mechanism).

Request to Send (RTS)

Used to condition the DCE for data transmission. The default level is high by internal pull up.

The exact behaviour of RTS is defined by an AT command. Software or hardware control can be selected. Hardware flow is the default control.

The application must pull RTS low to communicate with the modem. The modem will respond by asserting CTS low, indicating it is ready for communication.

Clear To Send (CTS)

CTS indicates that the DCE is ready to transmit data. The default level is high. You can define the exact behaviour of CTS through an AT command, and can select software or hardware flow control.

Owner’s Manual

Rev 1.0

Page 35 of 35