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80 Operation Theory
when the phase of the EA signal leads the phase of the EB sig-
nal.
A timing waveform is illustrated below.
Figure 4-33: A/B Phase Timing
CW/CCW Mode
In this mode, the pulse from EA causes the counter to count
up, while EB will cause the counter to count down.
OUT/DIR Mode
Z
In this mode, the pulse from EB decides on whether the
counter should increase or decrease, whereas EA count
the number of pulses.
Figure 4-34: OUT/DIR Pulses
The index input (EZ) signal of the encoder is used as the
“ZERO” index. This signal is common to most rotational
motors. EZ can be used to define the absolute position of the
mechanism. When a rising edge of EZ signal is received, it will
clear the encoder counter value to ‘0’.
Counter value read/write
To read the encoder counter value, use the get_cnt_value()
function. The parameter ‘*Value’ returns the counter value. To
set the encoder counter value, use set_cnt_value(). The
counter value will be set as the parameter ‘Value’.