VIPA System 200V IM Series, Руководство пользователя, Страница: 141 / 348

Manual VIPA System 200V
Chapter 4 Interbus
HB97E - IM - Rev. 06/29 4-5
Interbus is based upon a ring structure that operates as a cyclic shift
register. Every Interbus module inserts a shift register into the ring. The
number of I/O points supported by the module determines the length of this
shift register. A ring-based shift register is formed due to the fact that all
the devices are connected in series and that the output of the last shift
register is returned to the bus master. The length and the structure of this
shift register depend on the physical construction of the entire Interbus
system.
Interbus operates by means of a master-slave access method where the
master also provides the link to any high-level control system. The ring-
structure includes all connected devices actively in a closed communication
loop.
In comparison to client-server protocols where data is only exchanged
when a client receives a properly addressed command, Interbus
communications is cyclic in nature and data is exchanged at constant inter-
vals. Every data cycle addresses all devices on the bus.
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C o ntrol Loop Back
Protocol Overhead
Start of
Scan End of
Scan
Data Array
in out
IBS Master
IBS Slave
IBS Slave
IBS Slave
IBS Param
RS232
Process data
transfer