Rockwell Automation 1771-IJ_IK IK ENCODER/COUNTER MODULES - Manual (Page 9)

Chapter
1
Publication 1771ĆUM006B-EN-P - June 2002
Introduction
This publication describes installation, adjustments and the
programming necessary for communication between the
Encoder/Counter Module (cat. no. 1771-IJ,-IK) and a programmable
controller processor. The programming techniques given here enable
the processor to direct the operation of the encoder/counter module
and to monitor its status.
The encoder/counter module can be used with any Allen-Bradley
processor that uses the 1771 I/O structure.
Depending on the intended use of the encoder/counter module, two
different programming methods can be used. These methods are:
•
Single transfer programming
Use single transfer only if the module is in a local I/O chassis and
generally when not using preset words. (If using preset words
with single transfer, you must use multiplexing as described in
section titled Multiplexing in Chapter 5). If using single transfer,
disregard chapter 6 on block transfer.
•
Block transfer programming
Use block transfer any time. If using block transfer, disregard
chapter 5 on single transfer.
The encoder/counter module maintains a count, independent of the
processor, of input pulses that typically originate from such devices
as quadrature type encoders, high speed optical beam counters, and
certain types of switches. The module (Figure 1.1) is capable of
making decisions based on the count total by comparing it to
previously programmed values and activating either one or both of
its outputs based on the results of the comparison. The module can
also return the accumulated count to the processor for arithmetic
computations or display.
The module also provides inputs for a marker signal from an encoder
and a voltage level signal from a limit switch to allow for home
positioning. In the count mode, the direction of the count can be
changed either from the processor or, for speed critical application, at
the module itself through an external switch. The maximum
detectable input pulse frequency of the module is 50kHz.
General
General Description