Rockwell-automation 1769-HSC Compact High Speed Counter Module Manual de usuario descargar pdf (Pagina 25)

Rockwell Automation Publication 1769-UM006E-EN-P - July 2013 25

Module Operation Chapter 2

X1 Quadrature Encoder Mode Selection

In this mode, when a quadrature encoder is attached to inputs A and B, the count

direction is determined by the phase relation of inputs A and B. If A leads B, the

counter increments. If B leads A, the counter decrements. In other words, when 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 rising transitions on input A are ignored.

The counter changes value only on one edge of input A as shown in Figure 5.

For more information see

Direction Inhibit and Direction Invert Output

Control Bits on page 21 and their effect on Quadrature signals on page 27.

Table5-UpandDown Counting

Direction

Inhibit Bit

Direction

Invert Bit

Input A (count) Input B (direction) Change in

Count Value

00 0, 1,  1

0, 1,  -1

 0

01 0, 1,  -1

0, 1,  1

 0

10 0, 1,  1

0, 1,  1

 0

11 0, 1,  -1

0, 1,  -1

 0

TIP

When both A and B transition at the same time, instead of in the defined

90° phase separation, the quadrature signal is invalid.

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Rockwell-automation 1769-HSC Compact High Speed Counter Module Manual de usuario Pagina 25