ADLINK PCI-8164 - Manual (Page 129)

Operation Theory 117
4.4.2 Feedback position counter
The card has a 28-bit binary up/down counter managing the
present position feedback for each axis. The counter counts signal
inputs from the EA and EB pins.
It accepts two kinds of pulse inputs: Plus and minus pulse inputs
(CW/CCW mode), and; 90° phase shifted signals (AB phase
mode). The 90° phase shifted signals maybe multiplied by a factor
of 1, 2 or 4. 4x AB phase mode is the most commonly used in
incremental encoder inputs. For example, if a rotary encoder has
2000 pulses per phase (A or B phase), then the value read from
the counter is 8000 pulses per turn or –8000 pulses per turn
depending on its rotating direction. These input modes can be
selected using the _8164_set_pls_iptmode() function.
In cases where the application has not implemented an encoder, it
is possible to set the feedback counter source to generate the out-
put pulses, just as with the command counter. Thus, the feedback
counter and the command counter will have the same value. To
enable the counters to count the number of pulses inputted, set
the “Src” parameter of the software function
_8164_set_feedback_src() to 1.
Plus and Minus Pulses Input Mode (CW/CCW Mode)
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 cause the counter to count up,
whereas EB 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 difference
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.