Rockwell Automation 8520-MUM 9/Series CNC Mill Operation and Programming Manual Documentation Set - Manual (Page 407)

Axis Motion
Chapter 14
14-31
Although this command moves the axes at rapid feedrate as if in G00
mode, it is not modal. If G01, G02, or G03 modes are active, they will
only be temporarily canceled for the return to home moves.
Only the axes specified in the G28 block are moved. For example:
N1 G28 X4.0; the X axis is moved to home after moving to 4.0
N2 G28 X4.0 Y2.0; the X and Y axes are moved to home after moving to (4.0 ,2.0)
Figure 14.17
Automatic Return To Machine Home (G28)
Cutting tool
Y
X
Intermediate point
Machine home
Usually a G28 is followed by a G29 (automatic return from machine
home) in a part program; however, the control will store the intermediate
point in memory for be use with any subsequent G29 block executed
before power down. Only one intermediate point is stored for each axis.
When a G28 is programmed with a new intermediate point, any axis not
programmed in that block will remain at the old value. For example:
N1 G28 X4.0 Y3.0; Intermediate point X=4 Y=3
N2 G28 Y2.0; New intermediate point X=4, Y=2