CY545 Stepper System Controller
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© 2002 Cybernetic Micro Systems
Chapter 17 - CY545 Step Rate Information
77
Slope and Elapsed Time
While it is difficult to provide an exact formula for the CY545 acceleration behavior, due to the
complex nature of the stepping algorithm, we can provide an approximate formula. This should
be used as a general guide only, with actual values determined experimentally. The formula is
given by:
accel = a(s) =
dV(s) =
(3906 * D)
@12 MHz
dT(s)
(256 - s)
where
a(s)
is the acceleration in steps/second
2
s
is the slope parameter value
D
is the “distance” between two adjacent rates
in steps/second, the incremental slope
also, the ramp time is given by the acceleration and the dynamic range of step rates taken as:
t
...
=
...
|Rmax - R0|
...
=
|Rmax - R0|
a(s)
3906 * D)
(256 - s)
The value used for D in the above formulas must be chosen with care, since the distance
between rate points changes as you move through the CY545 Step Rate Table. D starts with a
value of 25, then 50, then 35, and finally inflects to larger values as we reach the digital
resolution limit of the CY545.
The following figures show typical performance under various values of slope, and may be used
as a general guide in selecting initial operating parameters. The figures are followed by the
CY545 Step Rate Table, which lists all 256 possible step rates when operating the CY545 with a
12 MHz clock.
