V.24 Port Sharing - ABB ETL600 Instruction Manual

ETL600
10 ms
9 bit
2 bit
Channels
The multiplexer detects the data transfer rate being used by MOD600
and automatically adjusts its own operation accordingly. If the the
DPLC modem reduces its data transfer rate due to poor transmission
conditions (fall-back), the data transfer rate of the aggregate channel
also has to be reduced and this means that the data transfer rates of
individual channels have to be reduced or the channels switched off.
Five different data transfer rate profiles for the aggregate channel and
each individual channel can be defined for this purpose.
External data terminals can be connected to the channels as follows:
•
One G.703 interface (not supported with ETL600 Release 1)
synchronous data transfer at 64 kbps;
•
Up to two V.11 interfaces for synchronous data transfer at data
transfer rates from 9600 up to maximum available datarate for
MOD600;
•
Up to six V.24 interfaces for asynchronous data transfer at data
transfer rates from 1200 to 19200 bps.
For details about the different data terminals refer to section 3.5.4.
3.5.3.2.

V.24 Port Sharing

This feature permits sharing of one modem transmission channel
(NSK600 or MOD600) with up to four V.24 port interfaces. Additional
switches allow the physical through-connection of available V.24 data
ports to available modem transmission channels (NSK600 modem or
MOD600 modem).
The implementation is based on simple channel broadcasting towards
all connected DTEs while data signals from the connected DTEs are
OR-wired. No collision detection has been implemented leaving it to
higher level protocols.
Typical applications for ports sharing are SCADA system that poll their
RTUs over the same transmission channel. With four possible ports
sharing one channel, the following applications are realizable:
•
Up to 4 local RTUs
•
Up to 3 local RTUs with one digital transit connection
•
Up to 2 local RTUs and two digital transit connections (T-line).
3.5.4. Data Port Interfaces
Different physical interfaces are provided for data communication:
each of the available interface type is suitable for specific transmission
formats.
Structure and Function
1KHW001489-EN
is the frame length;
is the preamble for synchronization of the frame;
are used for speed adjustment per each channel;
is the number of configured channels.
November 2005
ABB Switzerland Ltd
3-51