Basic Principles of Serial Data Transmission   
2.4 Data Transmission with the ASCII Driver 
  Point-to-point connection CP 440 Installation and Parameter Assignment 
40  Manual, 09/2007, A5E00057742-03 
2.4.4 Topologies Between the Communication Partners 
Applications 
The CP 440 can be used in different topologies in the RS422 and RS485 operating modes. 
Distinctions are drawn between connections with: 
●  Two nodes (point-to-point) and 
●  Several nodes (multipoint) 
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. 
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