PROFIBUS DP-Master

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5.4 Functionality of the FSPMM2-Task
This task provides the functionality of DP V1 Class 2 on layer 7 of the OSI/ISO layer model. The
acyclic data processing capabilities for Profibus DP Masters Class 2 provided by the FSPMM2-task
are described in this section.
The error handling is the same as already described for DP V1 Class 1, so please refer to section
5.3.2.2 “DP V1 Error Processing” above.
5.4.1 General Remarks on DP V1 Class 2
The DP V1 Class 2 technology is characterized by the following features:
• Connection-oriented data transmission over a DP V1Class 2 connection
• Connection must be established explicitly (‚initiated’) before first data transmission can take
place. A communication reference identifies the established connection from that time on.
• After that the services ‚Read’, ‚Write’ and ‚Data’ Transport are available.
• Connection must explicitly be de-established (‘aborted’).
• A master class 2 can only have one connection to a slave at a time.
• A slave may have multiple connections to a master class 2 and one to a master class 1 at a
time.
5.4.2 DP V1 Class 2 Masters
Class 2 masters have special capabilities when communicating with slaves such as:
• Reading the configuration data of the DP slave
• Reading the input and output data (but no write access possible)
• Address assignment to slaves
Class 2 masters are used for commissioning the network and for maintenance and diagnostic
purposes and may be removed after the start-up phase when the system is working correctly.
Class 2 masters acyclically communicate with slaves over a class 2 connection (also called MSAC_C2
connection relationship). This class 2 connection must explicitly be set up.
5.4.3 Basic Services for Connection Maintenance
Two services are defined for handling a class 2 connection between a class 2 master and a slave:
• MSAC2_Initiate service.
• This service is used by the DP master class 2 in order to set up a DP V1-Class 2 connection to
the DP slave. The DP slave then receives a “Initiate” indication.
• MSAC2_Abort service.
• This service is used by the DP master class 2 in order to abort a DP V1-Class 2 connection to
the DP slave. The DP slave then receives an abort indication. The DP slave may also request an
abort of the class 2 connection by itself. For instance, this can be accomplished by sending the
abort packet.
PROFIBUS DP-Master |
DOC061001API12EN | Revision 12 | English | 2010-12 | Released | Public © Hilscher, 2006-2010