User's Manual

Mode of operation
Siemens PLT 130
.
1994
2/3
Addressing, transmission modes
This method has the following important advantages:
There is far less loading on the bus system since only the
information is read from the automation system which is cur-
rently displayed on the monitor channels
Data need only be stored at one position as a result of the
distributed data base principle. Modifications are therefore
only necessary at one position
No special planning for the OS systems is required in the
automation systems (exception: curve display)
Acces to information in the automation systems by another
computer is possible without additional planning (by using the
function ”Read parameters”).
The cyclic data exchange is also used for a life test
of all partici-
pants connected to the CS 275 bus by an OS operation and
monitoring system. Each failure and also the return of a partici-
pant is supervised and signalled.
Sporadic data
transfer
Sporadic data transfer is necessary to rapidly pass on modifica-
tions in the process control system to other participants. Typical
examples are faults or changes in status (e. g. motor on/off)
which detects the automation system. Messages exchanged
between several automation systems are transmitted by means
of the coupling blocks MKS/MKE.
A status word is assigned to each function block for processing
with standardized operation and monitoring as well as to driver
blocks for I/O modules with standardized display. The changes
in signal are detected event-controlled by the status word or by
the MKS block, provided with the actual time (MKS only) and
transferred to the bus system. This then transfers MKS mes-
sages to a maximum of 6 participants (typically OS systems
and higher-level computers) which have ”registered” them-
selves for this information when the complete system was
started up. This presents the advantage that the automation
system need only transmit one message with one or several
destination addresses. In addition, only those stations receive
the information which actually require it.
Data trans fer with OS systems and computers takes place using
the functions ”Read parameters” and ”Write parameters”.
Fig. 2/2 Sporadic/acyclic data exchange, example OS/AS and AS/AS
Addressing
The addressing of the participants of the bus system is oriented
towards the transmission of messages between several autono-
mous buses and within a bus.
Each participant is identified by two addresses:
Bus address (0 to 7), i. e. 8 autonomous buses are possible.
7 bus couplers are needed in this case.
Participant address (0 to 99).
These two addresses are set on the local bus interface module
using jumpers or DIP switches.
The bus coupler behaves like a participant with respect to each
bus. It has an address on each bus.
Transmission modes
A differentation is made between two transmission modes when
configuring and defining the AKS and BKS transmitter blocks:
-- Direct coupling (DI)
-- Co mmo n data (CD).
Direct coupling
(DI)
The registered participants are directly addressed by the trans-
mitter blocks, i. e. each participant only receives the data which
is assigned for it. Up to 6 receivers can be registered with a
transmitter block and receive the data (analog or binary values)
pertaining to it with each transmission cycle of this block.
Any participant on the bus can be a receiver. Transmission can
also take place via bus couplers. A receiver is entered as such
in the transmitter block in the respective automation system.
The MKS block only operates in direct coupling mode.
Common-Data
(CD)
The transmitter block sends the data simultaneously to all con-
nected participants of a particular bus. Thus certain identical
data can be planned in a transmitter block for many participants
on a bus and many destination addresses can then be reached.
The CD procedure can only be used for subscribers with the
same bus address. Addressing via bus couplers is not possible.
The participants on a bus connected via a bus coupler can be
addressed via their own CD procedure.
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This catalog is out of date, see note on page 2