2 - counter modes, Introduction, Counter/encoder overview – Rockwell Automation 1756-HSC ControlLogix High Speed Counter Module User Manual
Page 17: Chapter 2, Counter modes, Introduction counter/encoder overview, Chapter
17
Rockwell Automation Publication 1756-UM007C-EN-P - November 2011
Chapter
2
Counter Modes
Introduction
This chapter describes the Counter modes for the 1756-HSC/B module.
Topics include:
• types of counting: counter and encoder.
• means of storing the counts.
• modes for manipulating the count.
• tags for control of on-board outputs.
There are three Counter modes that can be selected from the Operational
Mode pull-down menu on the Counter Configuration tab.
See
for configuration details.
The choices are:
• Counter mode (default).
• Encoder x1 mode.
• Encoder x4 mode.
Counter/Encoder Overview
The Encoder and Counter modes are virtually identical; the only difference is
the method used to count. There are two counters (using input A and B) per
module. Input Z, which is described in more detail later in this chapter,
basically affects how the counts are stored based on the selected Storage mode.
In Counter mode, the module reads incoming pulses from input A only and
stores the accumulated count value in the Present Value tag. The state of
input B determines whether to increment or decrement the count based on
whether it’s low, floating (count up) or high (count down).
In both Encoder modes, the 1756-HSC module uses two channels to read
incoming pulses. The module uses the phase relationship between
inputs A and B to determine the count value and direction of the rotation.
Topic
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