ADLINK PCI-8158 - Manual (Page 79)

Operation Theory 69
If you don’t use encoder for motion controller, the feedback source
for this counter must be set as pulse command output or the
counter value will always be zero. If it is set as pulse command
output, users can get the position counter value from pulse com-
mand output counter because the feedback pulses are internal
counted from command output pulses.
The following diagrams show these two types of pulse feedback
signal.
The pattern of pulses in this mode is the same as the Dual Pulse
Output Mode in the Pulse Command Output section except that
the input pins are EA and EB.
In this mode, pulses from EA pin cause the counter to count up,
whereas EB pin caused the counter to count down.
90° phase difference signals Input Mode (AB phase Mode)
In this mode, the EA signal is a 90° phase leading or lagging in
comparison with the EB signal. “Lead” or “lag” of phase differ-
ence between two signals is caused by the turning direction of
the motor. The up/down counter counts up when the phase of
EA signal leads the phase of EB signal.