CIP Services and User-created Tags
Rockwell Automation Publication 1756-PM020F-EN-P - January 2019 47
Message Reply Field Bytes (in hex) Description
34 5D 00 00 Last 32-bit Instance ID in this reply
0A 00
50 61 72 74 73 5F 44 65 73 74
16-bit Symbol Name Length
Characters in the symbol name
C3 00 Symbol Type
See also
CIP Services and User-created Tags on page 41
Step 1: Finding user-created controller scope tags in a Logix 5000
controller on page 45
Observe the analysis:
• The Reply Data includes the Instance ID along with the data values for
attributes 1 and 2.
• The Symbol Name attribute is a variable length structure of type
STRING that consists of a UINT character count followed by the
single octet characters (ASCII encoded) in the name.
• The Symbol Type attribute is a WORD, which is a 16-bit string,
representing the symbol data type that is described in the next step.
The example previously returned number of instances, starting with instance
0x0312 and ending with instance 0x5D34. Only instances that are created are
returned. Gaps in the instance numbers will occur.
Any symbol instances that represent tags whose External Access is set to
None are not included in the reply data.
See also
Continue the retrieval process on page 47
In this example, assume that the controller has too many symbols to fit in
one reply. The last instance number shown in the previous example is
0x5D34, and incremented to 0x5D35.
This table shows the request for the next set of instances or attribute data.
The value 0x5D35 is the starting instance ID in the path.
Message Request Field Bytes Description
Request Service 55 Get_Instance_Attribute_List Service (Request)
Request Path Size 03 Request Path is 3 words (6 bytes) long
Request Path 20 6B 25 00 35 5D Logical Segments: Class 0x6B, Instance 0 x5D35(starting instance)
Request Data 02 00 Number of attributes to retrieve
01 00 Attribute 1 – Symbol Name
Continue the retrieval process
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