In these cases the CP 440 can be used as:
• Master or
• Slave.
Figure 2-8 RS 422 Point-to-Point
Figure 2-9 RS 485 Point-to-Point
In the case of a master/slave topology, there must be an appropriate message frame in the user
program. Example: The master sends all the slaves a message frame with address information.
All the slaves listen in and compare the address with their own. If the address is the same, the
addressed slave sends its answer.
The senders of all slaves must be able to switch to low impedance.
RS422 Operation
In the case of a master/slave topology in RS422 operation:
• The master's sender is interconnected with the receivers of all the slaves.
• The slaves' senders are interconnected with the master's receiver.
• Only the receiver of the master and the receiver of one slave have a default setting. All the
other slaves function without default settings.
Basic Principles of Serial Data Transmission
2.4 Data Transmission with the ASCII Driver
Point-to-point connection CP 440 Installation and Parameter Assignment
Equipment Manual, 03/2022, A5E00057742-AE 33
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