AN2475 Freescale Semiconductor / Motorola, AN2475 Datasheet - Page 8

• Manufacturer Part Number: AN2475
• Description: Generating a PWM Signal Modulated by an Analog Input Using the MC68HC908QY4 Microcontroller
• Manufacturer: Freescale Semiconductor / Motorola

AN2475/D
8
YES
AND TURN ON RED LED
TURN OFF GREEN LED
INCREMENT PERIOD
ERROR STATUS!
PERIOD = $FF?
NO
Generating a PWM Signal Modulated by an Analog Input
YES
YES
Freescale Semiconductor, Inc.
For More Information On This Product,
SET RESOLUTION (D) TO ~6%
Using the MC68HC908QY4 Microcontroller
SET DUTY CYCLE TO ~50%
WAIT FOR REGULATION
AD = ADC INPUT VALUE
TURN ON GREEN LED
DECREMENT PERIOD
PWM INITIALIZATION
PERIOD < MINIMUM
AD = REGULATOR
AD < REGULATOR
(PERIOD • PWM)
Figure 4. Software Flowchart
VALUE?
VALUE?
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START
UNIT?
< = D?
NO
NO
NO
NO
YES
YES
INCREMENT PWM
DUTY CYCLE
PWM <= D?
NO
YES
NO
AD >= UPPER LIMIT?
AD < LOWER UNIT?
DECREMENT PWM
DUTY CYCLE
YES
YES
NO
MOTOROLA