Product specifications
R01AN0168ED0101 Rev. 01.01 13
Application Note
Chapter 3 About Stepper Motor Movement
3.2 The PWM Generation of ISM
Following a Prescaler (GTB), the central Time Base determines the PWM
output of ISM; this means that all PWM outputs of ISM are having the same
frequency and are all synchronous.
In order to avoid that too many edges are occurring at the same time on
several ports, each PWM output can be assigned to a delay, which is set in
clocks of the central time base (
CDVn and CDHn).
The level of the PWM is in the range 0 ... 2
10
- 1, where 0 means no PWM
output (0%), and 2
10
-1 sets the output level to full 100%. The zero level (0%)
output is important to allow to switch off the output completely. 100% level is
achieved, because the PWM compare value can be set one count more than
the range of counting of the timebase.
The duty cycle of the PWM is set by defining the values
CHPn and CVPn, for
each channel, for the horizontal and vertical PWM, respectively. As the
maximum count c of the Channel Timebase is 2
10
- 2, and the duty cycle is
given by a/(c+1), the following formula is given for the duty cycle P:
Figure 3-3 PWM Generation of ISM
P%
CHP
2
10
1–
------------------=
P%
CVP
2
10
1–
------------------=
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