Rockwell Automation 1336T ControlNet Frn1.02 Rev 1.5 - Manual (Page 49)

4–7 Using Unscheduled Messaging
Publication 1336 FORCE–5.18 ––March, 1999
PLCs use discrete transfer to transfer data to and from the
ControlNet Adapter Board during every rack scan. The ControlNet
Adapter Board transfers this data to and from the SCANport device.
The PLC’s use message blocks to perform emulated block transfer.
The descriptions provided in this chapter contain the configurations
necessary to set up the data files in the message transfer instructions.
Header and data values depend on the operation to be performed.
Also included is a description of the status word that is returned from
the drive and appears in the message transfer read header
information.
Emulated Block Transfer