MC68HC908MR8 Datasheet, PDF (157/372 Pages) Motorola, Inc – Microcontrollers

Pulse-Width Modulator for Motor Control (PWMMC)
Output Control
UP/DOWN COUNTER
MODULUS = 3
PWM VALUE = 2
PWM1 W/
NO DEAD-TIME
PWM2 W/
NO DEAD-TIME
PWM VALUE = 3
PWM VALUE = 2
PWM VALUE= 1
PWM1 W/
DEAD-TIME = 3
PWM2 W/
DEAD-TIME = 3
3
3
3
3
3
3
Figure 9-16. Dead-Time and Small Pulse Widths
9.6.3 Output Polarity
The output polarity of the PWMs is determined by two options: TOPNEG
and BOTNEG. The top polarity option, TOPNEG, controls the polarity of
PWMs 1, 3, and 5. The bottom polarity option, BOTNEG, controls the
polarity of PWMs 2, 4, and 6. Positive polarity means that when the PWM
is active, the PWM output is high. Conversely, negative polarity means
that when the PWM is active, PWM output is low. See Figure 9-17.
NOTE:
Both bits are found in the CONFIG register, which is a write-once
register. This reduces the chances of the software inadvertently
changing the polarity of the PWM signals and possibly damaging the
motor drive hardware.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor Pulse-Width Modulator for Motor Control (PWMMC)
Technical Data
157