Instruction Manual

Chapter 7 Counters
NI 6236 User Manual 7-16 ni.com
increment occurs on the rising edge of channel A. When channel B leads
channel A, the decrement occurs on the falling edge of channel A.
Figure 7-15. X1 Encoding
X2 Encoding
The same behavior holds for X2 encoding except the counter increments or
decrements on each edge of channel A, depending on which channel leads
the other. Each cycle results in two increments or decrements, as shown in
Figure 7-16.
Figure 7-16. X2 Encoding
X4 Encoding
Similarly, the counter increments or decrements on each edge of
channels A and B for X4 encoding. Whether the counter increments or
decrements depends on which channel leads the other. Each cycle results in
four increments or decrements, as shown in Figure 7-17.
Figure 7-17. X4 Encoding
Channel Z Behavior
Some quadrature encoders have a third channel, channel Z, which is also
referred to as the index channel. A high level on channel Z causes the
counter to be reloaded with a specified value in a specified phase of the
Ch A
Ch B
Counter Value
7
7
6
5
5
6
Ch A
Ch B
Counter Value
56 8
9
7
5
6 8
9
7
Ch A
Ch B
Counter Value 5 6 8 9 10 1011 1112 1213 137
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