ETIC MR1200, Руководство пользователя

Страница: 31 / 39

Operation
ETIC - MR1200 - USER MANUAL - 908709-02 Page 31
Duration of data emission
The MR1200 will continue transmitting data for a limited period of between 1 and 255 seconds ( tp_emi
parameter), after which the modem will pause for a period also of between 1 and 255 seconds ( tp_rec
parameter) to allow other modems to gain access to the radio channel.
If transmission time limits have been set, long messages should be segmented and sent by the terminal
in several batches, otherwise data may be lost.
modem memory capacity
The size of the MR1200's transmit buffer can be increased from 32 bytes up to 2 Kbytes depending on
the application.
4.3. Modem control modes
4.3.1. The terminal-modem interface
The MR1200 dialogues with its control terminal across a standard RS232 serial interface.
The following table describes :
- the circuits comprising the serial interface
- their function
- their use according to the operating mode chosen.
Circuit Name Pin Direction Function Control mode / implementation
automatic direct V25bis
102 SG 5 Signal ground yes yes yes
103 TD 3 terminal->modem Transmitted data yes yes yes
104 RD 2 modem->terminal Received data yes yes yes
105 RTS 7 terminal->modem Ready to send - yes -
106 CTS 8 modem->terminal Clear to send advised yes yes
107 DSR 6 modem->terminal Data set ready optional advised yes
108/2 DTR 4 terminal->modem Data terminal ready optional optional yes
109 DCD 1 modem->terminal Carrier detect optional optional optional
125 RI 9 modem->terminal Ring indicator optional optional optional
Its 4 control modes enable the MR1200 to be used with a large range of terminals making it easily
adaptable to particular user applications.
4.3.2. Automatic mode
In this mode, radio modem operation is transparent to the terminal, with only the 3 circuits 103-TD,
104-RD, and 102-SG being used. If necessary circuit 106-CTS may be implemented for handshaking
requirements.
Data transmission begins on detection of a specific character.
Rest
Circuit 106-CTS has an ON condition (logic 1), and circuit 109-DCD an OFF condition (logic 0).