Freescale Semiconductor MC68HC908MR32 - Manual (Page 133)

Output Control
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor 133
Figure 12-20. Top/Bottom Correction for PWMs 1 and 2
12.5.4 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
Figure 12-21 .
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.
PWM1
PWM2
PWM VALUE REG. 1 = 1 PWM VALUE REG. 2 = 2
IS1 POSITIVE IS1 POSITIVE IS1 NEGATIVE IS1 NEGATIVE
PWM = 1 PWM = 1 PWM = 2 PWM = 2