Справочник Пользователя для Motorola MC68HC908MR16
Pulse-Width Modulator for Motor Control (PWMMC)
Output Control
MC68HC908MR16/MC68HC908MR32 — Rev. 4.0
Advance Information
MOTOROLA
Pulse-Width Modulator for Motor Control (PWMMC)
157
9.6.4 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
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
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.
register. This reduces the chances of the software inadvertently
changing the polarity of the PWM signals and possibly damaging the
motor drive hardware.
Figure 9-20. PWM Polarity
UP/DOWN COUNTER
MODULUS = 4
PWM <= 0
PWM = 1
PWM = 2
PWM = 3
PWM >= 4
UP-ONLY COUNTER
MODULUS = 4
PWM <= 0
PWM = 1
PWM = 2
PWM = 3
PWM >= 4
CENTER-ALIGNED POSITIVE POLARITY
EDGE-ALIGNED POSITIVE POLARITY
UP/DOWN COUNTER
MODULUS = 4
PWM <= 0
PWM = 1
PWM = 2
PWM = 3
PWM >= 4
UP-ONLY COUNTER
MODULUS = 4
PWM <= 0
PWM = 1
PWM = 2
PWM = 3
PWM >= 4
CENTER-ALIGNED NEGATIVE POLARITY
EDGE-ALIGNED NEGATIVE POLARITY