MC68HC(7)05H12
—
Rev. 1.0
General Release Specification
MOTOROLA
Pulse Width Modulator (PWM)
159
L
G
R
General Release Specification — MC68HC(7)05H12
Section 14. Pulse Width Modulator (PWM)
14.1 Contents
14.2
14.3
14.3.1
14.4
14.4.1
14.4.2
14.4.3
14.4.4
14.5
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .159
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .160
PWM Channel Microshifting . . . . . . . . . . . . . . . . . . . . . . .161
Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .162
PWM Data Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . .163
PWM Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . .164
PWM Channel Enable Register. . . . . . . . . . . . . . . . . . . . .165
PWM Channel Polarity Register . . . . . . . . . . . . . . . . . . . .165
PWM During WAIT Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . .166
14.2 Introduction
The pulse width modulator (PWM) system has eight 8-bit channels.
Preceding the 8-bit (
÷
256) PWM counter is a programmable
prescaler.The PWM frequency is selected by choosing the desired
divide option from the programmable prescaler.
The four PWM channels 0 to 3 provide four full H-bridge drivers capable
of driving air core instruments or stepper motor instruments. Each of the
H-bridges will be implemented as a combination of one PWM power
driver and another general purpose output (GPO) port power driver. A
single PWM channel provides a pulse width ratio for the corresponding
PWM driver part of a single H-bridge. Thus the current through the
bridge can be controlled by the pulse width ratio.
The four PWM channels 4 to 7 with their power drivers can support four
90
°
(small angle) aircore instruments.