Rockwell Automation 8520-ARM2 9/Series CNC AMP Reference Manual Documentation Set - Manual (Page 186)

Servo Parameters
Chapter 7
7-40
Function
This parameter is used to configure which port will be receiving position
feedback.
You may choose to use optional feedback for position data. Optional
feedback can be used for:
a second feedback device to improve accuracy of a positioning axis
spindle feedback
analog servo feedback
9/230, 9/260, and 9/290 systems
With 9/230, 9/260 or 9/290 CNCs, typically this port should be selected as
the same port selected for the parameter Output Port Number.
Important: It is not a recommended configuration to use the analog out or
DAC output connector for servos that require feedback. This is due to the
increased amount of wiring necessary to return axis feedback to a different
connector (and is not available on CN8). It is typically much easier to
attach any axis including a spindle that has feedback to one of the normal
axis connectors and use that connector as the drive (Output Port
Number) and feedback connector (Position Loop Feedback Port).
If the axis being assigned a feedback port is to be connected to a second or
third servo module, the port numbers (and connector numbers) are the
same as for axes on the first servo module. The control determines
whether the axis is on the first or second module based on the AMP
parameters Number of Motors on 1st Board and Number of Motors on
the 2nd Board.
Important: All servo ports, Output Port Number, Position Loop
Feedback Port, and Velocity Loop Feedback Port, must be connectors
on the same servo module (1st, 2nd, or 3rd board).
Each servo module or 9/230 processor has three or four axis connectors
through which feedback data can be received.
Important: If using the three axis digital or analog servo card, port
assignments must be contiguous. For example, you cannot assign a
feedback device to J3 without having one assigned to J2.
7.2.11
Position Loop Feedback
Port