
3. ELECTRICAL DESCRIPTION
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LZT 123 7359 R1B
3.5.1 Serial 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.
3.5.2 Serial Data Signals - RD, TD
The default baud rate is 9.6kbps, however higher bit rates up to 460kbps
are supported and can be set by AT commands. At start-up the GM29
transmits and receives data at the default rate of 9.6kbps in either
standard AT mode or binary mode (the first received data - AT or binary
format - determines the operating mode).
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.
3.5.3 Control Signals - RTS, CTS, DTR, DSR, DCD, RI
RTS and CTS are capable of transmitting at 1/10th of the data
transmission speed for data rates up to 460kbps (byte-oriented 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.
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