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76 Operation Theory
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 mechnical 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.
4.5.4 General Purpose Counter
The source of general purpose counter could be any of the follow-
ing:
1. Command position output – the same as a command
position counter
2. Feedback position input – the same as a feedback posi-
tion counter
3. Manual Pulser input – Default settig
4. Clock Ticks – Counter from a timer about 9.8 MHz
4.5.5 Target Position Recorder
The target position recorder is used for providing target position
information. It is used in continuous motion because motion con-
troller need to know the previous motion command’s target posi-