Rockwell Automation 8520-ARM2 9/Series CNC AMP Reference Manual Documentation Set - Manual (Page 193)

Servo Parameters
Chapter 7
7-47
Figure 7.28
Connectors on Optional Feedback Module
(available only on the 9/260 and 9/290 3 Axis Digital servo card)
CN16F
CN15F
CN14F
Important: Even though the optional feedback module provides additional
feedback ports, there is still a maximum of 6 axes that can be configured
with feedback on the 9/260 and a maximum of 9 axes with feedback on the
9/290 when using the three axis servo boards. The optional feedback
module is used for the 3 axis digital servo modules only. The optional
feedback module is not available on the 9/230 or 9/440 controls.
Function
This parameter tells the control the type of position feedback device used
for the axis.
No Feedback -- The servo has no position feedback.
ABS Encoder on Dig. Mod. -- 8520 digital drives with 8500 digital
servos using an absolute encoder (not for 1326 servo systems).
If Allen-Bradley 8500 Series standard digital motors are used and they
have absolute encoders, this should typically be selected as the position
feedback type.
7.2.12
Position Feedback Type