Rockwell Automation 20-COMM-R Remote I/O Adapter - Manual (Page 61)

Using Block Transfer Messaging 5-3
20-COMM-R Remote Adapter I/O User Manual
Publication 20COMM-UM004D-EN-P
See Block Transfer Read Structure to Receive Block Transfer Messages on
page 5-4 for a description of each word in a Block Transfer Read used to
receive an Explicit Message response.
Block Transfer Write Structure to Send Block Transfer Messages
Data Field Description
Word 0 Length
The least significant byte contains the length of the Explicit Message. The most
significant byte is always zero. This is the length of the actual message in bytes, not
the size of the BTW in words.
This length excludes the two bytes of word 0, but includes words 1 and 2, and all of
the data in the main body of the message to be sent. If using a scattered read or
write with class code 0x93, the length includes the zero(s) after the last parameter as
place holders. See pages C-9 … C-14 .
Word 1 0x81 and DPI Port
The least significant byte contains the value 0x81. The most significant byte is the
DPI port. For PowerFlex drives, you can access:
0 - Drive
1 - Device at Port 1 (HIM)
2 - Device at Port 2
3 - Device at Port 3
4 - Device at Port 4
5 - Device at Port 5 (adapter)
6 - Device at Port 6
Word 2 CIP Service
The least significant byte contains a CIP service. The most significant byte is always
zero (0). CIP services include the following:
0x0E - Get Attribute Single
0x10 - Set Attribute Single
0x4B - Get Attributes Scattered
0x4C - Set Attributes Scattered
Word 3 CIP Class
See Appendix C , CIP Objects for a list of classes.
Word 4 CIP Instance
See Appendix C , CIP Objects for an instances in each class.
Word 5 CIP Attribute
See Appendix C , CIP Objects for a list of attributes in each class.
Word 6…19
Word 6…29
Word 6…59
Data or Padding
Data required for the message. The message must be either 20 words, 30 words, or
60 words. If it is not, pad the message with zeros.