CY545 Stepper System Controller
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CHAPTER 17 - CY545 STEP RATE INFORMATION
CY545 Step Rate Information
Step rates for the CY545 are chosen from the CY545 Step Rate Table, which appears at the
end of this section. Selections for the starting rate are made by the value of the First Rate (F)
parameter, and selections for the slewing rate are made by the value of the Rate (R) parameter.
Each rate parameter value acts as an index into the CY545 Step Rate Table, which has 256
unique entries, ranging from a parameter value of zero to 255. Thus, for any crystal clock
frequency, the CY545 can generate 256 different step rates. The CY545 Step Rate Table is
shown for a clock frequency of 12 MHz, so the specified rates must be linearly scaled by the
actual clock frequency when a different clock is used. The scaling factor is Fcy/12, where Fcy is
the operating frequency, in megahertz.
As an example, the following commands would select a starting rate of 200 steps per second,
and a final rate of 10000 steps per second, if the CY545 is operated at 12 MHz.
F 8
R 203
200 steps per second initial rate
10000 steps per second final rate
The Slope Parameter
When the CY545 is commanded to step through a motion, by either the Go or Position
commands, stepping will start at the rate selected by the F parameter. The rate will then
increase regularly through the other rates in the table, until the final rate, selected by the R
parameter is achieved. The CY545 will then slew at this rate until it is time to decelerate back to
the selected starting rate as the specified number of steps is taken.
If the travel distance is too short to achieve the final rate, the CY545 will perform a partial
acceleration, going to the highest rate possible before decelerating back to the starting rate.
The speed at which the CY545 changes from one rate to the next is selected by the Slope (S)
parameter. The value of S can range from 1 to 255, with 1 representing the slowest
acceleration, and 255 representing the fastest acceleration.
For any particular application, the stepping parameter values, including the slope, are best
determined experimentally when you are looking for the operating limits of the system. Each
motor size, driver type, and load combination will have different performance limits. In general,
the required range of step rates is known for a particular application, and will determine the
values for F and R, but the acceleration value is not so easily specified.
© 2002 Cybernetic Micro Systems
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Chapter 17 - CY545 Step Rate Information
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