Multi Master System

A PROFIBUS network containing several DP masters is called a multi-master system. Up to 32 stations (DP masters and DP slaves) can be operated on one bus segment. Using repeaters the system can be expanded to up to 126 stations. In a multi-master system no data exchange between the DP masters is performed. The entire system is divided into logical subsystems inside of which one DP master communicates with the assigned DP slaves. Each DP slave can be assigned to only one DP master. The master has unlimited access to its assigned slaves while all other masters on the bus can only read the input and output data of these slaves.

All DP masters of class 1 (normal bus master, here: AC500) and class 2 (commissioning device, typically a PC) can read the input and output data of all slaves.

Additionally the DP masters of class 1 and class 2 have the following access possibilities to their assigned DP slaves. They are able to:

• Parameterize DP slaves (e.g. timing supervision, bus interchange).
• Configure DP slaves (e.g. type / number of channels).
• Write output data of the DP slaves.
• Read diagnosis data of the DP slaves.
• Send control commands to the DP slaves (e.g. freezing input signals).

A DP master of class 2 is additionally able to:

• Read and write configuration data of the class 1 DP masters.
• Read configuration data of the DP slaves.
• Read diagnosis data of the class 1 DP masters.
• Read out the diagnosis data of the DP slaves assigned to the respective DP master.

Multi master system example