Rockwell Automation 57C422B 2 Axis Servo Module - Manual (Page 49)

PROGRAMMING 4-21
Note that the strobed gearing registration position (registers
86,87) and the current gearing position (registers 76, 77)
data are not affected by the selections made in register 38. X
and Y axis gearing registration and current gearing position
values will always be strobed from their respective hardware
encoder channels.
Bit 2 in register 38 selects the format of the gear ratio. The
default (0) is a 32-bit number stored in registers 25,26 scaled
by 16777216. Setting bit 2 to 1 allows you to express the
gear ratio as a ratio of two 16-bit numbers in registers 25 and
26. See section 4.20 for more information.
Bit 3 in register 38 enables ramp velocity control on the
follower axis when the master axis is moving and gearing is
enabled, when you are changing from the non-geared to the
geared mode, or when the gear ratio is changed while
gearing is enabled. This command will limit the rate of
acceleration and deceleration until the axis is synchronized
with the master. Note that this limit applies only to trapezoidal
acceleration, not to S-curve acceleration. Once the axis is
synchronized with the master, there is no limit on
acceleration/deceleration through register 38, bit 3. When
ramped velocity control is selected, if gearing is disabled
while the follower axis is still moving, the follower axis will
continue to move at that velocity until a stop motion
command is issued in register 66, bit 6.
4.30 Registers 39, 40: Backlash
Compensation
Registers 39 and 40 are used to store a signal value (in
counts) that selects the amount of backlash compensation.
The sign of the value corresponds to the approach direction.
Refer to figure 4.29.
For example, a value of +20 entered here will mean that an
incremental move of 100 counts will result in an actual move
of 100 counts and then a stop. The same move in the
negative direction will result in the axis moving - 120 counts,
+20 counts, and then a stop.