IMO i3C Lite, User Manual

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CHAPTER 12: HIGH SPEED I/O (HSC/PWM)
12.1 Overview
In addition to the compliment of simple analog and digital I/O, the
i ³C Lite supports High Speed
Counting (HSC) I/O functions and may support Pulse Width Modulation (PWM) Output functions. The
HSC functions include frequency, totalizing, pulse width, and quadrature measurement.
The PWM functions include traditional PWM (with variable rate and duty) with variable acceleration
and deceleration rates.
To determine function availability, refer to the associated model’s
Specification/Installation sheet (Digital DC Input/Output sections).
This chapter describes the operation of these high level I/O functions. For configuration details of
these functions, see
Chapter 15 , i ³ Config Configuration.
12.2 Glossary of High Speed I/O Terms
Table 12.1 – Glossary of High Speed I/O Terms
Accumulator Register used to accumulate or store up a sum or count of many items or events.
Clear
A special function to zero out the value in a specific register. (Not used with Frequency or
Period Measurement.)
Disable A special function to prevent the counter from running.
Encoder A sensor or transducer for converting rotary motion or position to a series of electronic pulses
Frequency
Input
The number of times an electromagnetic signal repeats an identical cycle in a unit of time,
usually one second.
Latch (strobe)
A special function that uses a digital logic circuit to store one or more bits. A latch has a data
input, a clock input and an output. When the clock input is active, data on the input is "latched"
or stored and transferred to the output register either immediately or when the clock input
goes inactive. The output retains its value until the clock goes active again.
Marker
Input into the I³ that indicates a particular position. Typically, an encoder has a marker output
that represents a specific point in the rotation.
Polarity
A Polarity pull-down box is associated with each function and indicates the manner in which
the trigger happens (e.g., High level, Low Level, Falling Edge, Rising Edge).
Preload
(load)
A special function used to trigger loading of a value into a register upon an event. (Not used
with Frequency or Period Measurement.)
Quadrature
A high-speed device that expresses the phase relationship between two periodic quantities of
the same period when the phase difference between them is one fourth of a period. A coupler
in which the two output signals are 90° out of phase.
Totalizer
A counter that sums the total number of cycles applied to its input.