PROFIBUS Manual

The publisher broadcasts cyclic data to all bus users. To do this, the following conditions must be satisfied:

 

During initialization of cyclic data exchange in the Set_Parameter telegram, the class 1 DP master (controller) marks in byte 8  the bit: "slave should work as publisher".

 

Simultaneously, the min TSRD is set to 37 tBit. This ensures that the publisher's response is delayed by at least the 33 bit times for a SYN and is therefore recognized by all bus users as the beginning of a new telegram sequence.

 

With cyclic data, the master replaces the SRD service with the MSRD service and function code 7. The slave responds with function code 8 or 10 and addresses the reply to broadcast address 127.

 

The ability of a DP slave to work as a publisher is shown in the GSD file with the key word

 

Publisher_supp = 1

 

For this purpose, GSD syntax revision 3 is a minimum requirement.

 

Please note:

These publisher functions are very easy to implement. Most ASICs from Siemens include publisher functions, even if the manufacturer has not enabled them. Therefore, in the case of simple field devices with no processor (e.g. devices produced with an LSPM2) the GSD can be supplemented with the key word Publisher_supp and the publisher function switched on by an appropriate master!