Rockwell Automation 1747-SN Remote I/O Scanner - Manual (Page 79)

1 Publication 1747-UM013B-EN-P - January 2005
Chapter
5
RIO Block Transfer
This chapter contains the following information:
• RIO block transfer theory of operation
• RIO block transfer general functional overview
• scanner’s block transfer buffer layout
• detailed operation of RIO block transfer
• RIO block transfer application considerations
• steps for setting up a block transfer
• quick reference for using status and control bits
• block transfer control logic examples
RIO Block Transfer Theory
of Operation This section provides a conceptual overview of block transfer as it
pertains to SLCs, RIO scanners, and remote devices. For specific
functionality details, refer to Using Block Transfer Instructions (BTR
and BTW) on page 5-5.
What Is RIO Block Transfer?
RIO Block Transfer is a data transfer mechanism that allows you to
control the transfer of up to 64 words of data to or from a remote
device over the Allen-Bradley RIO link. A Block Transfer Read (BTR)
is used when a remote device transfers data to the SLC. A Block
Transfer Write (BTW) is used when an SLC processor writes data to a
remote device.
The diagrams on the following pages illustrate the concepts of how
block transfers occur using an SLC processor, an RIO scanner, and a
remote device. The first diagram illustrates the path a block transfer
follows. The second and third diagrams illustrate in greater detail the
theory of operation of a BTR and a BTW, respectively.