3 parameter protocol – Rockwell Automation MD65 Profibus Communication Card User Manual
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Using Explicit Messaging (Parameter Protocol)
7-3
7.3
Parameter Protocol
This protocol uses four words in the PROFIBUS I/O area. Requests
and responses are a handshake procedure and cannot be batched,
meaning that if the master sends a request, it has to wait for the
response before sending a new request.
With this protocol you can:
•
Read 8-bit or 16-bit parameters from any MDI port
•
Write 8-bit or 16-bit parameters to any MDI port
•
Read the Module Fault Code
•
Read Events
•
Read Diagnostic Items
Refer to sections 7.3.1 and 7.3.2 for a description of the data that is
required in each word.
Figure 7.2 – Parameter Message Format
Bit
15-12
11
10-0
15-12
11
10-0
Parameter Access
Word 1 (PCA)
RC
SPM
PNU
RC
SPM
PNU
Parameter Access
Word 2 (IND)
Subindex
Subindex
Parameter Access
Word 3 (PVA)
Spare
Spare
Parameter Access
Word 4 (PVA)
Parameter value
Parameter value
Request
Response