Automationdirect.com DL05, User Manual

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High-Speed Input and Pulse Output Features
3–18
High-speed Input and Pulse Output Features
Mode 20: Quadrature Counter
The counter in the HSIO circuit can count two quadrature signal pulses instead of a
single pulse train (mode 10 operation). Quadrature signals are commonly generated
from incremental encoders, which may be rotary or linear. The quadrature counter
has two ranges from 0 to 99999999 or -8388608 to 8388607. Using CT76 and CT77,
the quadrature counter can count at up to a 5 kHz rate. Unlike Mode 10 operation,
Mode 20 operation can count UP or DOWN, but
does not feature automated preset
values or “interrupt on external reset” capability. However, you have the standard
ladder instruction preset of CT76.
The diagram below shows HSIO functionality in Mode 20. When the lower byte of
HSIO Mode register V7633 contains a BCD “20”, the quadrature counter in the HSIO
circuit is enabled. Input X0 is dedicated to the Phase A quadrature signal, and input
X1 receives Phase B signal. X2 is dedicated to reset the counter to zero value when
energized.
Output Circuit
Input Circuit
CPU
PLC
DL05
X0
Y0, Y1
X3- X7
Y2 - Y5
VĆmemory
V7633 0020
Mode Select
I/O data
HSIO
COUNTER
Phase
A
Phase
B
X2
Reset
X1
Quadrature encoder signals contain position and direction information, while their
frequency represents speed of motion. Phase A and B signals shown below are
phase-shifted 90 degrees, thus the quadrature name. When the rising edge of
Phase A precedes Phase B’s leading edge (indicates clockwise motion by
convention), the HSIO counter counts UP. If Phase B’s rising edge precedes Phase
A’s rising edge (indicates counter-clockwise motion), the counter counts DOWN.
90
°
phase shift
Phase A
Phase B
Leading Edge Signal
Phase A
Phase B
Leading Edge Signal
Clockwise sequence
Counterclockwise sequence
one cycle
Purpose
Functional Block
Diagram
Quadrature
Encoder Signals