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1 General
Industrial buses
General quality specifications
•
Security
Data must not be falsified or get lost without an error message being displayed
•
Performance
The communication performance must meet the requirements
•
Functionality
The functions (services) required by the user have to be provided in the required
quality
•
Uptime
Communication systems are often major parts of a system, and the uptime of the
entire system can depend on them to a large extent
•
Cost-effectiveness
The cost / performance ratio must be reasonable.
In addition to the general quality specifications, additional requirements apply to communication
systems in the process automation environment.
Additional quality specifications for process data communication systems
•
Ability to respond
Data must proceed from the transmitter to the receiver within a defined period of time,
which is usually very short.
•
Trouble-free operation
Operation in close proximity to power installations must be possible. The system must
adequately resist mechanical and climatic stresses.
1.1
Definition of terms
1.1.1
Computer link
A computer link enables the exchange of data and control information between computers and
controls (e.g. CAD, FMS, ... , NC, RC, SPS ... , as shown in figure SINEC H1) on the initiative
of a computer, control system or operator. The data exchange mainly covers workpiece
programs, tool data, workpiece data, control functions (e.g. NC start, NC stop), operating data
such as status messages, alarm and error messages.
A computer link can be realised using a bus connection or using one of many serial
connections.
The following figure shows the SIEMENS computer systems used for CAD, FMS,
NC Archive and PPC as well as the RC, NC and PLC systems on a common bus cable. If
older systems are to be connected to the bus, e.g. SINUMERIK System 8, this is done via a
gateway station.
1–2
© Siemens AG 1989 All Rights Reserved
06.91
6FC5 197-0AB20-0BP0
SINUMERIK 840/880 (PJ)
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