Command Segmentation - Anybus CompactCom 40 EtherNet/IP Network Manual

C.2 Command Segmentation
When a command message is segmented, the command initiator sends the same command header mul-
tiple times. For each message, the data field is exchanged with the next data segment.
Please note that some commands cannot be used concurrently on the same instance, since they both
need access to the segmentation buffer for that instance.
Command segmentation is used for the following commands:
• Set_Configuration_Data (see "Command Details: Set_Configuration_Data" on page 167)
• Send (see "Command Details: Send" on page 120)
• Send To (see "Command Details: Send_To" on page 121)
Segmentation Control bits (Command)
Bit Contents
0 FS
1 LS
2 AB
3...7 (reserved)
Segmentation Control bits (Response)
Bit Contents
0...7 (reserved)
When issuing a segmented command, the following rules apply:
• When issuing the first segment, FS must be set.
• When issuing subsequent segments, both FS and LS must be cleared.
• When issuing the last segment, the LS-bit must be set.
• For single segment commands (i.e. size less or equal to 255 bytes), both FS and LS must be set.
• The last response message contains the actual result of the operation.
• The command initiator may at any time abort the operation by issuing a message with AB set.
• If a segmentation error is detected during transmission, an error message is returned, and the cur-
rent segmentation message is discarded. Note however that this only applies to the current seg-
ment; previously transmitted segments are still valid.
Anybus CompactCom 40 EtherNet/IP
Doc.Rev. 1.5
Meaning
Set if the current segment is the first segment
Set if the current segment is the last segment
Set if the segmentation shall be aborted
Set to 0 (zero).
Meaning
Ignore.
Message Segmentation 190
Doc.Id. HMSI-27-212