Table of Contents
Advertisement
General
Output Words - Block
Transfer
Block Transfer Programming
Block transfer programming is available with all Allen-Bradley
processors that use the 1771 I/O structure.
Block transfer is specifically intended for use with I/O modules such
as the encoder/counter module, that perform more complex
operations than simple on/off input sensing or output switching. For
the operation of such modules, multiple words of data must be
transferred to or from the processor.
Block transfer can be particularly useful with the encoder/counter
module when more than one word must be output to the module, that
is, when one or both preset words are used. By using block transfer
in these applications, you can avoid any involvement with
multiplexing techniques for module/processor communication.
Multiplexing techniques are used in single transfer programming, as
described in chapter 5. Note, however, that single transfer
techniques can be the easiest to use in any application where only a
single output control word must be sent to the module. For this
reason, when not using any of the preset words, use single transfer
programming for module/processor communication.
The material for block transfer is organized as follows:
•
Section titled Output Words - Block Transfer describes the
configuration of output words when using block transfer.
•
Section titled Example Block Transfer Programs describes
block transfer ladder logic for PLC -2, PLC-3, and PLC-5 family
processors.
The output control and preset words have a unique configuration
when block transfer programming has been selected. Initially, the
program must set the bit combinations of these words to the proper
arrangement for the application. Then, through block transfer, these
words are transmitted to the encoder/counter module.
Output Control Word
Figure 6.1 shows the configuration of the output control word for
block transfer. By setting bits in this word, you set up the initial
mode of module operation and change it as required during
operation.
Chapter
Publication 1771 UM006B-EN-P - June 2002
6
Advertisement
Table of Contents
