Rockwell Automation 8520-ARM2 9/Series CNC AMP Reference Manual Documentation Set - Manual (Page 119)

Home Parameters
Chapter 5
5-17
The following outlines automatic machine homing (G28) for a DCM axis
that has been previously homed:
1. Execute a G28 block, either through the part program or MDI. The
axis moves at a direction determined by the parameter G28 Direction
to Home and a speed determined by the rapid feedrate. All feedrate
overrides are disabled throughout an automatic homing sequence.
Important: The axis does not repeat the homing routine of moving to the
limit switches and searching for the encoder marker.
2. The axis moves to machine home via an intermediate point. The
control stores this intermediate point specified by the axis word in
memory to be used as the point of return for the automatic return
from machine home operation called out by G28.
The return operation generates two axis moves both executed at the
rapid feedrate: to the intermediate point and to the axis home
position.
Important: DCM axis homing must be performed manually or by
programming a G28. Attempting to program any motion command other
than a G28 will result in the decode error “MUST HOME AXIS”.
For more information regarding Automatic Return to Machine Home
(G28), refer to the Axis Motion chapter in your 9/Series CNC Operation
and Programming Manual.
Function
This parameter specifies the initial direction the axis moves while
searching for the home limit switch during an automatic homing
operation (G28).
If the axis has already been homed when the G28 is commanded, this value
is not used. Refer to your programming and operation manual for
more information.
Important: Special PAL programming or operator instruction may be
required to position the axis on the correct side of the home limit switch
when a G28 is executed.
5.2.1
G28 Direction to Home