Installation manual

1 Publication 1747-RM001G-EN-P - November 2008
Chapter 8
Block Transfer Instructions
This chapter contains general information about block transfer instructions
and explains how they function in your application program. Each of the block
transfer instructions includes information on:
• what the instruction symbol looks like.
• how to use the instruction.
Block Transfer Instructions
(BTR and BTW)
Block transfer instructions are supported by SLC 5/03 (OS302, Series C),
SLC 5/04 (OS401, Series C) and SLC 5/05 (OS501, Series C) and higher
processors using RSLogix 500 version 4.10 and higher. With block-transfer
instructions, you can transfer up to 64 words to or from a remote device over
an Allen-Bradley Remote I/O (RIO) link. A Block Transfer Read (BTR) is
used to receive data from a remote device. A Block Transfer Write (BTW) is
used to send data to a remote device. The RIO Series B scanner (1747-SN)
modules and the back-up scanner (1747-BSN) modules perform block
transfers via M0 and M1 file buffers.
A false-to-true rung transition initiates a BTW or BTR instruction. The BTW
instruction tells the processor to write data stored in the BTW Data File to a
device at the specified RIO rack/group/slot address. The BTR instruction tells
the processor to read data from a device at the specified RIO rack/group/slot
address and store it in the BT Data File. The Data File may be any valid
integer, floating point or binary data table file. A total of 32 block transfer
buffers are available; you can execute a maximum of 32 different block
transfers. Each buffer is made up of 100 consecutive words. The processor
runs each block transfer request in the order it is requested. When the
processor changes to Program mode, all pending block transfers are cancelled.
Table 8.1 Block Transfer Instructions
Instruction Mnemonic Instruction Name Purpose Page
BTR Block Transfer Read A BTR is used to receive data
from a remote device.
8-1
BTW Block Transfer Write A BTW is used to send data to a
remote device.
8-1
EN
DN
ER
BTW
Block Transfer Write
Rack 0
Group 0
Slot 0
Control Block N10:10
Data File N20:0
Buffer File M0:1.100
Requested Word Count 0
Transmitted Word Count 0
BTW
Fixed SLC
5/01
SLC
5/02
SLC
5/03
SLC
5/04
SLC
5/05
•••