VIPA PC-CPU 486, Manual

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Manual VIPA PC-CPU 486 Chapter 4 Deployment of the PC-CPU
HB111E - Rev. 02/32 4-17
As transfer medium Profibus uses an isolated twisted-pair cable based
upon the RS485 interface.
The RS485 interface is working with voltage differences. Though it is less
irritable from failures than a voltage or a current interface. You are able to
configure the network as well linear as in a tree structure.
At the front side of your PCs is a 9pin slot. Via this slot you connect the
coupler as master directly into your Profibus network.
For every segment a max. of 32 participants is allowed. The single
segments are connected together via repeaters. The max. segment length
depends on the baudrate.
Profibus uses a baudrate between 9.6kBaud and 12MBaud, the slaves are
following automatically. All participants of the network are communicating
with the same baudrate.
The bus structure under RS485 allows an easy connection resp.
disconnection of stations as well as starting the system step by step. Later
expansions don’t have any influence on stations that are already
integrated. The system realizes automatically if one partner had a fail down
or is new in the network.
The picture shows a Profibus connection under RS485 with outlined
terminating resistors:
L2P
Screen
Master Slave
3
8
L2P
3
8
Screen
L2N
L2N
Transfer medium