Communications configuring
3-138
System- and communication configuring D7-SYS - SIMADYN D
Edition 12.2003
3.13 USS master coupling
The USS master coupling defines an access technique, according to the
master-slave principle for data communications via a serial bus.
•
A multi-point-capable coupling is supported
•
Master-slave access technique
•
Single-master system
•
1 master and a maximum of 31 slaves
•
Bus line: Line without any branching
The master addresses the individual slaves using an address character in
the telegram. A slave can never initiate data transmit. Individual slaves
cannot transfer data directly between themselves.
The following SIMADYN D communications utilities can be connected to
the USS master coupling:
•
Process data
•
Message system
•
Display control
•
Parameter processing
3.13.1 Hardware
structure
The following hardware is required for the USS master coupling:
•
CS7 communications module with an SS4 communications module
(USS master). The interface is an RS485 interface (SS31 interface
sub-module).
The bus cable must be terminated at both ends. A 150
Ω
resistor is
connected between the RS485P and RS485N data signal lines at the first
and last nodes.
If a node is not transmitting, then the bus has an undefined potential,
because all transmitters are switched into the high-ohmic state. To
suppress signal faults in this status, a basis network is connected to the
bus so that it has a defined positive signal level. The basis network
should be connected at the nodes where the bus cable ends.
General
Features
Mode of operation
SIMADYN D
communication
utilities
Hardware required
Bus termination
Basic network
