ABB S900 Manual - Slave Address

I/O System S900 

Communication Interface for PROFIBUS DP, CI920 

4. Communication via PROFIBUS DP V1 

Slave address 

Conventions 

Up to 127 stations can be addressed via the PROFIBUS. However, only 32 

stations may be run on each line without using a repeater. Since at least one 

master must exist on the bus, the maximum slave address range is 126. Note 

that diagnostic or configuration devices connected only temporarily to the bus 

(Class_2 masters) must be taken into account as well! Address 0 must not be 

used for slaves. Address 126 is reserved for commissioning slaves whose 

address can be configured via the PROFIBUS. When using two 

communication interfaces (redundancy), the permissible PROFIBUS address 

range is limited to 1...124., since the redundant CI920 receives a PROFIBUS 

address made up of the active CI920 address +n (with n being configurable). 

Do not assign the same bus address to two stations. This will cause a crash of 

cyclic data transfer on both stations! 

Setting the bus address 

The setting is made via three coding switches on the termination unit. 

The new address will only be active upon a CI920 restart. After changing an 

address always remove and plug in again the CI920, or switch off the station 

for a short time.  

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