Datasheet

Chapter 11 Pulse Width Modulator with Fault Protection (PMF15B6C) Module
MC9S12E256 Data Sheet, Rev. 1.10
372 Freescale Semiconductor
Figure 11-60. Correction with Negative Current
11.4.5.4 Output Polarity
Output polarity of the PWMs is determined by two options: TOPNEG and BOTNEG. The top polarity
option, TOPNEG, controls the polarity of PWM0, PWM2 and PWM4. The bottom polarity option,
BOTNEG, controls the polarity of PWM1, PWM3 and PWM5. Positive polarity means when the PWM is
active its output is high. Conversely, negative polarity means when the PWM is active its output is low.
The TOPNEG and BOTNEG are in the configure register. TOPNEG is the output of PWM0, PWM2 and
PWM4. They are active low. If TOPNEG is set, PWM0, PWM2, and PWM4 outputs become active-low.
When BOTNEG is set, PWM1, PWM3, and PWM5 outputs are active-low. When these bits are clear, their
respective PWM pins are active-high. See Figure 11-59 and Figure 11-60.
Figure 11-61. PWM Polarity
11.4.6 Software Output Control
Setting output control enable bit, OUTCTLx, enables software to drive the PWM outputs rather than the
PWM generator. In an independent mode, with OUTCTLx = 1, the output bit OUTx, controls the PWMx
DESIRED LOAD VOLTAGE
BOTTOM PWM
LOAD VOLTAGE
TOP PWM
UP/DOWN COUNTER
PWM = 0
PWM = 1
PWM = 2
PWM = 3
PWM = 4
EDGE-ALIGNED
MODULUS = 4
UP/DOWN COUNTER
PWM = 0
PWM = 1
PWM = 2
PWM = 3
PWM = 4
MODULUS = 4
UP COUNTER
PWM = 0
PWM = 2
PWM = 3
PWM = 4
PWM = 1
MODULUS = 4
CENTER-ALIGNED
POSITIVE POLARITY POSITIVE POLARITY
UP COUNTER
PWM = 0
PWM = 2
PWM = 3
PWM = 4
PWM = 1
MODULUS = 4
CENTER-ALIGNED
NEGATIVE POLARITY
EDGE-ALIGNED
NEGATIVE POLARITY