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polled, a certain, selectable number of stations are polled in the subcycle. Following this, all
the stations in the main cycle are polled again.
MPI
The multipoint interface (MPI) is the programming device interface of SIMATIC S7. Devices
with an MPI interface (for example a TIM), can also communicate with each other (MPI bus).
Multimaster polling with time slots
When stations need to communicate with more than one master station in dedicated line or
wireless operation, the multimaster polling with time slots mode is used. Each of the
connected master stations is assigned one or more defined time slots per minute for polling.
The master stations then have their turn to poll in every minute.
Node station
A node station is a station that receives messages are from lower-level stations and forwards
them to other destination partners, substations (direct communication) or master stations.
OPC
(OLE for Process Control)
OPC includes a series of specifications for data exchange in automation engineering
between controllers, alarm transmitters etc. and control systems.
Organizational message
Organizational messages are used to execute organizational system functions.
These include, for example:
● General requests
● Time synchronization
● Counted value storage
● Coordinated connection establishment and termination in a dial-up network
● Message indicating station startup and station failure
● Requests for and transmission of subscriber records
Parameter assignment
A device is assigned the parameters it requires for starting up when it is supplied with data.
Permanent call
A permanent call does not interrupt the normal polling cycle; it is always executed alternating
with the standard poll from the normal polling cycle.
SINAUT ST7 Station control system - System Manual
System Manual, 05/2007, C79000-G8976-C178-06
Glossary
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