ADLINK PCI-8134A - Manual (Page 68)

58
• Operations
4.4
The Encoder Feedback Signals (EA, EB, EZ)
The PCI-8134/PCI-8134A has a 28-bits binary up/down counter for
managing the present position for each axis. The counter counts signals
input from EA and EB pins.
It can accept 2 kinds of pulse input: (1). plus and minus pulses
input(CW/CCW mode); (2). 90
° phase difference signals (AB phase mode).
90
° phase difference signals may be selected to be multiplied by a factor of
1,2 or 4. 4x AB phase mode is the most commonly used for incremental
encoder input. For example, if a rotary encoder has 2000 pulses per phase
(A or B phase), then the value read from the counter will be 8000 pulses per
turn or –8000 pulses per turn depends on its turning direction. These input
modes can be selected by set_pls_iptmode() function.
To enable the counters counting pulses input from (EA, EB) pins, set
“cnt_src” parameter of software function set_cnt_src() to 1.
Plus and Minus Pulses Input Mode(CW/CCW Mode)
The pattern of pulses in this mode is the same as Dual Pulse Output Mode
in Pulse Command Output section, expect that the input pins are EA and
EB.
In this mode, pulse from EA causes 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 90
° phase leading or lagging in comparison
with EB signal. Where “lead” or “lag’ of phase difference between two
signals is caused by the turning direction of motors. The up
/down counter
counts up when the phase of EA signal leads the phase of EB signal.
The following diagram shows the waveform.