LM628 Programming Guide
Introduction
The LM628/LM629 are dedicated motion control processors.
Both devices control DC and brushless DC servo motors, as
well as, other servomechanisms that provide a quadrature
incremental feedback signal. Block diagrams of typical
LM628/LM629-based motor control systems are shown in
Figures 1, 2
As indicated in the figures, the LM628/LM629 are bus pe-
ripherals; both devices must be programmed by a host pro-
cessor. This application note is intended to present a con-
crete starting point for programmers of these precision
motion controllers. It focuses on the development of short
programs that test overall system functionality and lay the
groundwork for more complex programs. It also presents a
method for tuning the loop-compensation PID filter. (Note 1)
Reference System
is a detailed schematic of a closed-loop motor
control system. All programs presented in this paper were
developed using this system. For application of the pro-
grams in other LM628-based systems, changes in basic
programming structure are not required, but modification of
filter coefficients and trajectory parameters may be required.
I. Program Modules
Breaking programs for the LM628 into sets of functional
blocks simplifies the programming process; each block ex-
ecutes a specific task. This section contains examples of the
principal building blocks (modules) of programs for the
LM628.
Note 1:
For the remainder of this paper, all statements about the LM628 also
apply to the LM629 unless otherwise noted.
01086001
FIGURE 1. LM628-Based Motor Control System
01086002
FIGURE 2. LM629-Based Motor Control System
National Semiconductor
Application Note 693
Steven Hunt
January 1999
LM628
Programming
Guide
AN-693
© 2002 National Semiconductor Corporation
AN010860
www.national.com
