IP-QUADRATURE modular

Description

Product Description
IP-Quadrature provides high density, cost-effective flexible implementation of four quadrature
decoder channels. Channels may also be used as general purpose counters. Four independent
channels provide 24-bit resolution, programmable modes, programmable polarity, interrupt
capability, differential or single-ended (RS-422 or TTL/CMOS) input, read-on-the-fly capability, and
a count frequency of 0 to 10 MHz.
Quadrature encoders are popular sensors that provide accurate, low cost incremental motion sensing.
Most commonly, they are shaft encoders that provide 512 to 2048 counts per revolution. They are
also commonly used as linear encoders with resolutions down to 0.005 inch. They are available in
nearly any length desired. Most encoders are now optical, using molded assemblies consisting of a
pair of LEDs, lenses, photo-sensors, and simple electronics. For rotary motion the assembly senses
alternating opaque and clear lines on a rotating wheel. For linear motion the alternating lines may be
on a fixed bar and the sensor assembly moves, or vice-versa. The pair of LED and photo-sensors are
offset about one-half line width so that direction of motion may be sensed by observing the relative
phase of the two outputs. Typical quadrature encoder outputs are a pair of digital logic signals that
are nominally 90° out of phase. Some encoders also provide an “index” pulse output once per
revolution to provide absolute position information. Most modern encoders run from +5 volts and
provide CMOS/TTL logic outputs and/or RS-422 differential logic outputs. RS-422 is
recommended where possible because of its inherent noise immunity and the ability to run long
distances. TTL logic levels should normally be restricted to cables less than ten feet in length.
Quadrature encoders are available from Hewlett-Packard, US digital, and other sources.
The general purpose input structure permits differential input from line drivers (RS-422 levels) or
single-ended logic level input (“TTL”) directly from most sensors. Programmable TTL resistive
terminators provide for flexible high-quality signal termination.
There are three inputs per channel. For normal quadrature operation the two quadrature inputs are
called X and Y. These inputs are sometimes called A and B lines from encoders. The X and Y inputs
are normally driven 90° out of phase. There is also a control input on each channel called Z. Its
function is programmable, but it typically operates, if used, as an index or latch input.
There is a programmable prescaler for each channel that may be set for X1, X2 or X4 operation.
Vectored interrupts are fully supported. Interrupts are individually maskable. Selectable conditions
are interrupt on borrow and interrupt on match (compare).
RS-422 differential input lines are normally terminated with 120? resistors. Users may remove these
socketed resistor networks or replace them with a different value if desired.
Each channel consists of a programmable input section, a 24-bit up/down counter block, a 24-bit
capture/match register, and a 24-bit output latch. The output latch permits accurate “on-the-fly”
reading of quadrature position values. The capture/match register may be used as either a hardware
“capture” register to record exact mechanical position or to provide an interrupt an any arbitrary
programmable quadrature position value.
The all CMOS design is inherently low power. Up to 16 quadrature channels may be implemented in
one host system slo

IP-QUADRATURE