Rockwell Automation 8520-GUM 9/Series CNC Grinder Operation and Programming Manual Documentation Set - Manual (Page 417)

Axis Motion
Chapter 12
12-45
CSS axis selection depends on what type of machine you have, the axis
configuration for that machine and the specific grinding application.
Surface grinding -- the spindle is typically selected as the CSS axis.
This results in CSS calculations being based on the distance from the
spindle centerline to the diameter at which the grinding wheel is being
used or dressed
Cylindrical grinding, S--word controls part spindle -- the CSS axis is
typically the axis perpendicular to the part centerline. This results in
CSS calculations being based on the distance from the part centerline to
the diameter being ground on the part
Cylindrical grinding, S--word controls wheel spindle -- the CSS axis
is typically the axis perpendicular to the part centerline both when
grinding the part and when dressing the wheel. This allows
implementation of CSS during part grinding and wheel dressing
CSS axis assignment is determined by your system installer in AMP. The
CSS axis can be changed by programming a P--word (P0 through P9) in the
G96 block when activating CSS.
Each P--word corresponds to a specific axis assigned to it in AMP. Any
CSS axis changes made by programming a P--word in the G96 block
remain in effect regardless of what mode the control is in. The default
CSS axis is assigned to P0 and is active on power-up and after a control
reset.
Your system installer can assign the spindle to be the CSS axis by entering
S as the CSS axis in AMP. If S is assigned to a P--word, it can also be
activated through the G96 block. When active (typically for surface
grinders), it determines surface speed based on the current wheel diameter
value described on page 21-9.
12.5.6
CSS Axis Selection