Rockwell Automation 1336T PLC Comm. Adapter, Series B, FRN 2.xx-3.xx - Manual (Page 147)

Chapter
7
Publication 1336 FORCE–5.13 –– September, 1998
Block Transfer Services
Chapter 7 provides the following information:
•
a description of block transfer
•
a description of the block transfer status word
•
block transfer message structures
PLC controllers use discrete transfer to transfer data to and from the
PLC Communications Adapter Board during every rack scan. The
PLC Communications Adapter Board transfers this data to and from
the SCANport device.
PLC controllers use block transfer to transfer data that does not
require continuous updates. To perform this function, the PLC
Communications Adapter Board provides a status word to the PLC
during the normal discrete transfer scan. This status word occupies
the first module group in the PLC I/O image table for the designated
rack. The PLC program then uses the status word to control the
Block Transfer Write (BTW) and Block Transfer Read (BTR)
functions of the PLC controller.
The descriptions provided in this chapter contain the configurations
necessary to set up the data files in the block 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 block transfer read header information.
Chapter Objectives
Block Transfer