Rockwell Automation 1746-HSCE2 Multi-Channel High Speed Counter Module - Manual (Page 24)

Publication 1746-UM002B-EN-P - August 2004
2-4 Module Operation
X1 Quadrature Encoder
When a quadrature encoder is attached to inputs 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 A
as shown in Figure 2.4 on page 2-5.
X2 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 input A, as
shown in Figure 2.4 on page 2-5.
X4 Quadrature Encoder
Operation is similar to the X2 Quadrature Encoder configuration,
except the counter changes value on the rising and falling edges of
inputs A and B as shown in Figure 2.4.
TIP
If B is low, the count increments on the rising edge
of input A and decrements on the falling edge of
input A. If B is high, all transitions on input A are
ignored.