ADLINK PCI-8154 - Manual (Page 87)

Operation Theory 77
4.5.2 Feedback position counter
The feedback position counter is a 28-bit binary up/down counter.
Its input source is the input pulses from the EA/EB pins. It counts
the motor position from motor’s encoder output. This counter
could be set from a source of command position for an option
when no external encoder inputs.
The command output pulses and feedback input pulses will not
always be the same ratio in mini-meters. Users must set the ratio if
these two pulses are not 1:1.
Because our motion controller is not a closed-loop type, the feed-
back position counter is just for reference after motion is moving.
The position closed-loop is done by servo motor driver. If the servo
driver is well tuned and the mechanical parts are well assembled,
the total position error will remain in acceptable range after motion
command is finished.
4.5.3 Command and Feedback error counter
The command and feedback error counter is used to calculate the
error between the command position and the feedback position.
The value is calculated from command subtracting feedback posi-
tion.
If the ratio between command and feedback is not 1:1, the error
counter is meaningless.
This counter is a 16-bit binary up/down counter.