MC9S12E256 Datasheet, PDF (361/602 Pages) Freescale Semiconductor, Inc – HCS12 Microcontrollers

Chapter 11 Pulse Width Modulator with Fault Protection (PMF15B6CV2)
For a given PWM pair, whether the odd or even PMFVAL register is active depends on either:
• The state of the current status pin, ISx, for that driver
• The state of the odd/even correction bit, IPOLx, for that driver
To correct deadtime distortion, software can decrease or increase the value in the appropriate PMFVAL
register.
• In edge-aligned operation, decreasing or increasing the PWM value by a correction value equal to
the deadtime typically compensates for deadtime distortion.
• In center-aligned operation, decreasing or increasing the PWM value by a correction value equal
to one-half the deadtime typically compensates for deadtime distortion.
In the complementary channel operation, ISENS selects one of three correction methods:
• Manual correction
• Automatic current status correction during deadtime
• Automatic current status correction when the PWM counter value equals the value in the PWM
counter modulus registers
Table 11-47. Correction Method Selection
ISENS
Correction Method
00
No correction¹
01
Manual correction
10
Current status sample correction on pins IS0, IS1, and IS2 during deadtime²
11
Current status sample on pins IS0, IS1, and IS2³
At the half cycle in center-aligned operation
At the end of the cycle in edge-aligned operation
1 _{The current status pins can be used as general purpose input/output ports.}
2 _{The polarity of the ISx pin is latched when both the top and bottom PWMs are off. At the 0%}
and 100% duty cycle boundaries, there is no deadtime, so no new current value is sensed.
3 _{Current is sensed even with 0% or 100% duty cycle.}
NOTE
Assume the user will provide current status sensing circuitry causing the
voltage at the corresponding input pin to be low for positive current and high
for negative current. In addition, it assumes the top PWMs are PWM 0, 2,
and 4 while the bottom PWMS are PWM 1, 3, and 5.
MC9S12E256 Data Sheet, Rev. 1.08
Freescale Semiconductor
361