Motorola M68HC08 - Manual (Page 158)

User Guide
Designer Reference Manual DRM028 — Rev 0
158 User Guide MOTOROLA
For current sampling period setting follow the label
CAN_CHANGE_PERCURSAMP_n in const.h file.
Current sampling period setting is provided by:
/* CAN_CHANGE_FPWM_n: */
/* CAN_CHANGE_PERCURSAMP_n: */
#define SET_PER_CS 2.0
Range: <1,->
The final current sampling period [
µs] is:
(EQ 6-16.)
current sampling period = PWM period * SET_PER_CS [
µs]
PER_CS_T1_US = PERIOD_PWM_US * SET_PER_CS [
µs]
6.5.7.3 Current Sampling Instant
Time period from a PWM reload event (middle of central aligned PWM)
to current sampling (time shift of A/D conversion with PWM) [
µs]:
/* CAN_CHANGE_PERCURSAMP_n: */
#define PER_PWM_CS_US 5.0
Range: <-PERIOD_PWM_US/2,PERIOD_PWM_US/2>
Usually it is not recommended to change PER_PWM_CS_US, but it can
be evaluated when there are problems with back-EMF zero crossing
noise.
It is necessary to set SET_PER_CS according to the following equation:
(EQ 6-17.)
6.5.8 Conclusion Software Parameters Setting and Tuning
If all the points in Tuning for Customer Motor are done, the software
should be customized to customer motor.
If the software customizing of your motor was not successful, it is
recommended that you read
Application Suitability Guide , since the
Current sampling period PWM period*SET_PER_CS =
PERIOD_PWM_US
2
---------------------------------------------------- – PER_PWM_CS_US PERIOD_PWM_US
2
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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