Rockwell Automation 57C422B 2 Axis Servo Module - Manual (Page 64)

4-36 2-Axis Servo Module M/N 57C422B
set by the next occurrence of the gearing registration input,
and the gearing position will be stored in registers 86, 87.
This bit is not set unless the "gearing registration enable" bit
in register 67 is set first. The gearing registration sensed bit
stays high (1) until the "gearing registration enable" bit is
toggled.
The gearing marker sensed bit is reset by the "reset gearing
position" command in register 66. If the gearing marker pulse
has been selected in register 2, the bit will be set by the next
occurrence of the gearing marker pulse.
The command acknowledge bit is set by the module to
indicate that a command in either register 66 or 67 was
recognized by the module. When this bit is set, you should
clear the command in register 66 or 67.