490 Rockwell Automation Publication 1444-UM001D-EN-P - June 2018
Appendix A CIP Objects
Advanced CM Data and Record Requests - Recommendations for Network Side
Implementation
• DataRequest Packet
• DataResponse Packet (with estimated processing time)
•Wait
• First RecordRequest Packet
• First RecordResponse Packet
The data is returned in multiple packets as an array of records of size
RecordSize. A significant amount of data can be returned depending on the
extent of the data requested. The recommended way to handle this data
transfer is to store the payload to a file for later retrieval.
It is recommended to store the first packet request and response packet to the
file. Thereafter, store the record array payload that is contained within each
subsequent packet. If this procedure is followed, the packet arrangement
within the file is as follows:
• RecordRequest Packet
• RecordResponse Packet (with first packet payload at the end)
– Second Response Packet payload
– Subsequent Response Packet payloads
• Last Response Packet payload
Instigate further sessions to retrieve data from any other required buffers or
channels. It is not necessary to reissue a fresh DataRequest.
Record retrieval from the file can then be accomplished as follows.
1. Open the file.
2. Read a record with size of Advanced CM Record Request from the head
of the file.
3. Access the BufferSelect variable to determine the type of record the file
holds.
4. Read a record with size Advanced CM Record Response from the file
pointer.
5. Access the RecordSize variable to determine the size of the record.
6. Start at the address of the first Record in the Data Array in the first
Advanced CM Record Response. To index to any record, use the
RecordSize to seek to the correct point in the file.
7. Read out the record of size, RecordSize.
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