Rockwell Automation 8520-ARM2 9/Series CNC AMP Reference Manual Documentation Set - Manual (Page 194)

Servo Parameters
Chapter 7
7-48
Important: Absolute encoders are not not compatible with the analog
servo interface. You should not select this feedback type when
configuring an analog servo interface.
INC Encoder U/V/W on Dig. Mod. -- for 8520 digital and motors
using an incremental encoder.
U/V/W refers to the special feedback channels in this encoder necessary
for initial commutation of the motor. If Allen-Bradley standard digital
motors are used and they have incremental encoders, this should
typically be selected as the position feedback type.
Analog system can also use these encoders. However, the U, V, and W
channels cannot be connected. The A, B, and Z channels for the
encoder are handled the same way as a normal incremental encoder with
a narrow marker (Z < A).
INC Encoder A/B/Z (Z < A) -- for a narrow marker differential
incremental encoder (sometimes called a “gated” encoder). Z < A refers
to a narrow marker pulse. This means that there is only one period
during which the A, B and Z channels can simultaneously be high.
Select this feedback type if using Allen-Bradley bulletin 845H encoders.
Refer to Figure 7.29 for examples.
Digital systems only use this selection if using a position feedback
device other than the encoder attached to the digital servomotors.
INC Encoder A/B/Z (Z > A) -- for a wide marker differential
incremental encoder (sometimes called a “non-gated” encoder). Z > A
refers to a wide marker pulse. This means that there is more than one
period during which the A, B, and Z channels can simultaneously be
high. Refer to Figure 7.29 for examples.
Digital systems only use this selection if using a position feedback
device other than the encoder attached to the digital servomotors.
A Quad B No Marker — Use this if your feedback device has no
marker (typically a glass slide type device). Be aware that this type of
device cannot be homed and therefore cannot establish an absolute
position (relative positioning only).
A Quad B with One Marker — Use this if your linear feedback device
(typically a glass slide type device) has a marker located near your home
limit switch.