Yaskawa LEGEND-MC - Manual (Page 354)

Operation
Symptom Cause Remedy
Controller rejects command.
Responded with a ? Anything. Interrogate the cause with TC
or TC1.
Motor does not start or
complete a move. Noise on limit switches stops
the motor. Noise on the abort
line aborts the motion. To check the cause,
interrogate the stop code
(SC). If caused by limit
switch or abort line noise,
reduce noise.
During a periodic operation,
motor drifts slowly. Encoder noise Interrogate the position
periodically. If controller
states that the position is the
same at different locations it
implies encoder noise. Also
use a scope to see the noise.
Reduce noise. Use differential
encoder inputs.
Same as above. Programming error. Avoid resetting position error
at end of move with SH
command.