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Rockwell Automation Publication 1444-UM001D-EN-P - June 2018 401
CIP Objects Appendix A
Also note that a data communication session starts at the first service request
and ends after the final response of the exchange. However, it is subject of an
(inactivity) timeout of 30 seconds.
0x4F Transient Record Request
Transient data is retrieved using a series of request/response unconnected
messages. One service is used to both start and continue with a session. The
first request initiates the session and subsequent requests return values that the
service returns. When the packet count down value that is returned reaches 0,
the session is completed.
The instance and attribute can be set to 1, but they are ignored.
The host sends the following Transient Record Request Parameters as part of
an 0x4F service request. This process is identical to the Data Manager Object
(0x38B), Service 0x4C CM Buffer Upload. Both services call the same service
handling code. That code is why the buffer select codes do not overlap with the
codes for the Data Manager Object.
Table 127 - Object Specific Services
Service
Code Implementation Service Name Description of Service
Class Instance
0x4B x x Reset transient buffer 0 Buffer-specific controls
0x4C x x Reset transient buffer 1
0x4D x x Reset transient buffer 2
0x4E x x Reset transient buffer 3
0x4F - x Transient Buffer Upload See “0x4F Transient Record Request”
Table 128 - 0x4F Transient Record Request
Byte Offset
Within Structure Structure Member Data Type Description
0 BufferSelect INT Specify the buffer to retrieve the data from:
• eOVERALL_TD0 (10), eFFT_TD0 (11),
• eTWF_TD0 (12), eTACHOL_TD0 (13),
• eOVERALL_TD1 (14), eFFT_TD1 (15),
• eTWF_TD1 (16), eTACHOL_TD1 (17),
• eOVERALL_TD2 (18), eFFT_TD2 (19),
• eTWF_TD2 (20), eTACHOL_TD2 (21),
• eOVERALL_TD3 (22), eFFT_TD3 (23),
• eTWF_TD3 (24), eTACHOL_TD3 (25)
The BufferSelect does not change during a session.
2 RequestedCount UINT RequestedCount = 0 returns all records in the buffer.
RequestedCount = 1 returns the most recently collected record.
Any other positive count returns that number of records from the buffer. If the count is greater than the max
available records, the max available records is returned instead.
The RequestedCount does not change during a session.
4 SessionInstance USINT The SessionInstance is initially specified as 0, but on subsequent calls the SessionInstance returned in CM
Record Response must be passed here.
5 ChannelSelect BYTE 4 Bits indicating the source channel. The ChannelSelect does not change during a session.
This field is ignored for all overall buffer types (eOVERALL_TD0, eOVERALL_TD1, eOVERALL_TD2,
eOVERALL_TD3)