Spectrum Controls SLC 500, User Manual

Page: 28 / 66

3-4 Chapter 3: Configuring the 1746sc-CTR4/CTR8
User’s Manual Pub. 0300181-07 Rev. A
Uni-Directional
With this configuration, the input increments in an upward direction. All 8
channels may be configured in the unidirectional mode. Every clock pulse will
increment the counter on the rising edge.
NOTE
The direction of the counter may be inverted by setting the Count
Direction bit described in the Configuration chapter.
Bi-Directional
The bidirectional counter requires 2 input channels. In this mode one channel is
used as the counter input and the second channel is used to determine the count
direction. The counter will increment when the Direction Channel value is 0 and
will decrement when the Counter Direction Channel value is 1.
X1 Quadrature Encoder
The quadrature mode requires 2 input channels. When a quadrature encoder is
attached to an input channel pair, A and B, the count direction is determined by
the phase angle between inputs A and B. If A leads B, the counter increments. If
B leads A, the counter decrements. (The counter changes value only on one edge
of input 1.) The counter increments once per quadrature cycle.
NOTE
The X1 Quadrature mode provides additional Anti-Jitter circuitry. This
distinguishes between a valid quadrature sequence and an invalid
sequence due to electrical noise or jitter. Jitter can occur if a quadrature
encoder stops rotating right at an input sensor trip point. This can cause
additional unwanted clock pulses. The X1 quadrature mode can detect
invalid transitions and filter these out.
X4 Quadrature Encoder
Like the X1 quadrature encoder, the count direction is determined by the phase
angle between inputs A and B. If A leads B, the counter increments. If B leads A,
the counter decrements. However, the counter changes value on the rising and
falling edges of inputs A and B. The counter increments four times per
quadrature cycle.