JYTEK NuDAQ PCI-69222, User Manual

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60 Operation Theory
X1 Encoder Mode
In X1 encoder mode, if phase A (EA0/EA1) is advanced of
phase B (EB0/EB1) in a quadrature cycle, the increment of
counter value will be 1. Otherwise, if phase B is advanced of
phase A in a quadrature cycle, the decrement of counter value
will also be 1.
Figure 4-33 shows a quadrature cycle and the increment and
decrement of counter value in X1 encoder mode. When phase A
leads phase B, the counter value increases on the first rising edge of
CLK after phase A goes high. When phase B leads phase A, the
counter value decreases on the first rising edge of CLK after phase A
goes low.
Figure 4-33: X1 Encoder Mode
X2 Encoder Mode
This mode is similar to X1 Encoder Mode, except that the
amount of counter value increases or decreases by two. Refer
to Figure 4-34.
Figure 4-34: X2 Encoder Mode