beautypg.com

Motorola M68HC08 User Manual

Page 158

background image

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

----------------------------------------------------

<

<

F

re

e

sc

a

le

S

e

m

ic

o

n

d

u

c

to

r,

I

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

n

c

.

..