FP Modem-EU Technical Manual
4.2 Multipoint Operation
5. Activate the multipoint mode with DIP switches 1, 2 and 3 as described
above, but leave DIP switch 4 OFF
If you want to use an FP-Sigma PLC for Multipoint communication via FP
Modem-EU, you must use the FP Modem-EU V1.2 or higher because the
FP-Sigma does not support a baud rate of 1200 bps.
4.2.2 Description of Multipoint Operation
After power-up or after switching on DIP 2, the message CONNECT is output via RS232C and
the modem is in multipoint online receive mode (high impedance). In receive mode, all modems
are listening and all data received via the communication line is passed on to the RS232C
interface without being checked for errors.
There are three different multipoint modes available for sending data:
1. PC/RTS mode:
In PC/RTS mode the receive/send changeover is controlled by the connected device
(PLC) via an RTS handshake signal. First the RTS signal is activated; then data is sent
to the modem. When all data has been sent, the RTS should be deactivated.
2. PLC mode:
In PLC mode all data via RS232C is collected by the modem until the end character (see
register S94) has been received. Then the modem switches to send mode and transfers
all characters it has buffered. After that the modem returns to receive mode.
3. Transparent mode (V1.21):
Similar to the PLC mode, the modem buffers all data received via RS232C. If the
modem receives no data for the idle time specified (see register S95), the modem
switches to send mode and transfers all characters it has buffered. After that the modem
returns to receive mode.
For transparent mode a S95 value of 1...255 is needed (increments of 3.3ms). The S95
can be set by the terminal or with DIP1 (S95=3=10ms). If the factory default of S95=0 is
used, PLC mode is entered!
In PLC and transparent mode, the RS232C buffer size is 32 KB.
In send mode, the modem's DCD output signals that data is being sent on the cable network,
hence any PLC that is connected will wait to receive data and not send simultaneously.
A changeover into command mode with the help of the escape sequence is not possible.
The FP Modem-EU multipoint frequency modulation is fully compatible with the industrial
standard V.23 Mode 2 (half-duplex with 1200 bps via two-wire cable). This is especially useful
for IEC60870-5-101 communication with the IEC60870-Communicator-Unit.
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