mc9s12e256 Freescale Semiconductor, Inc, mc9s12e256 Datasheet - Page 364

• Manufacturer Part Number: mc9s12e256
• Description: Hcs12 Microcontrollers 16-bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Chapter 11 Pulse Width Modulator with Fault Protection (PMF15B6CV2)
11.4.5.3
A current sense pin, ISx, for a PWM pair selects either the odd or the even PWM value registers to use in
the next PWM cycle. The selection is based on user-provided current sense circuitry driving the ISx pin
high for negative current and low for positive current.
Previously shown, the current direction can be determined by the output voltage during deadtime. Thus, a
simple external voltage sensor can be used when current status is completed during deadtime, ISENS =
10. Deadtime does not exists at the 100 percent and zero percent duty cycle boundaries. Therefore, the
second automatic mode must be used for correction, ISENS = 11, where current status is sampled at the
half cycle in center-aligned operation and at the end of cycle in edge-aligned operation. Using this mode
requires external circuitry. It actually senses current direction.
364
PMFCNT = PMFMOD
Current-Sensing Correction
IN DEADTIME
Pin
IS0
IS1
IS2
ISx PIN
PWM CYCLE START
PWM CYCLE START
ISx PIN
Figure 11-57. Internal Correction Logic when ISENS = 10
Figure 11-58. Internal Correction Logic when ISENS = 11
INITIAL VALUE = 0
INITIAL VALUE = 0
Table 11-49. Top/Bottom Current-Sense Correction
EVEN PWMVAL REGISTER
Logic State
EVEN PWMVAL REGISTER
ODD PWMVAL REGISTER
ODD PWMVAL REGISTER
PWM CONTROLLED BY
PWM CONTROLLED BY
PWM CONTROLLED BY
PWM CONTROLLED BY
D
D
CLK
CLK
0
1
0
1
0
1
MC9S12E256 Data Sheet, Rev. 1.08
Q
Q
D
D
CLK
CLK
PMFVAL0 controls PWM0/PWM1 pair
PMFVAL1 controls PWM0/PWM1 pair
PMFVAL2 controls PWM2/PWM3 pair
PMFVAL3 controls PWM2/PWM3 pair
PMFVAL4 controls PWM4/PWM5 pair
PMFVAL5 controls PWM4/PWM5 pair
Q
Q
A
B
A
B
A/B
A/B
Output Control
GENERATOR
GENERATOR
DEADTIME
DEADTIME
TOP PWM
BOTTOM PWM
TOP PWM
BOTTOM PWM
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