Rockwell Automation 8520 9/Series CNC Integration Maintenance Manual Documentation Set - Manual (Page 152)

Section 4B
Connecting the 3-axis Servo Module
4B-6
The 8520 Digital Servo Module is mounted in the component enclosure. It
functions as a high-speed servo processor. The control sends positioning
and velocity data to the servo module where it is processed to generate the
necessary pulse width modulated (PWM) command signals. These signals
are sent to the digital servo amplifier, which power the servo motors of the
control. The digital servo module also provides an analog velocity
command signal for a servo (typically the spindle) that is not using a
digital servo amplifier.
Figure 4B.5
Servo Module
CN13
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11276-I
The digital servo module receives two forms of feedback:
position data from the feedback devices on the axes
current feedback from the servo amplifier
It combines this position and current feedback data with the interpolated
commands from the control to generate the PWM command signals that it
outputs to the servo amplifiers.
4B.2
8520 Digital Servo Module
(8520-ENC3)