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9.3.5 Quadrature
Quadrature mode uses two HSC inputs, any of the four HSC inputs can be assigned for this
purpose.
Quadrature mode works much like the totalizer except the accumulator will automatically
increment or decrement based on the rotation phase of the two inputs. See the following
example for more details. Quadrature inputs are typically used for reporting the value of an
encoder.
Two modes are available for quadrature that select whether the accumulator counts up or down
when the phase of Input 1 leads Input 2. Check your encoder’s documentation to determine the
output form it uses or try both modes to determine if the encoder counts up when expected.
Figure 9.5
–
Quadrature
Using the above waveforms and a HSC
input configuration of “Quadrature”
-
“1 leads 2, count
up,” the accumulator
will count up when 1 is rising and 2 is low, 1 is high and 2 is rising, 1 is
falling and 2 is high, and when 1 is low and 2 is falling. This results in 4 counts per revolution.
So in order to determine the number of cycles, the accumulator would have to be divided by 4.
Marker reset operation is configured in the special operations and can be assigned to any of
the 4 high speed inputs or can be assigned to be controlled by a “Q” bit in ladder.
NOTE: The quadrature mode enables the Disable, Latch, Preload, Clear and Marker special
functions. Refer to the
for a description of these functions.
90°
phase
shift
1
(leading)
2
(lagging)
