MC68HC908LB8_05 Datasheet, PDF (148/234 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Pulse Width Modulator with Fault Input (PWM)
direction register. In order to read the states of the pins, the data direction
register bit must be a 0.
LDFQ1:LDFQ0 = 00 (RELOAD EVERY CYCLE)
UP-ONLY
COUNTER
LDOK = 1
MODULUS = 3
PWM VALUE = 1
PWMF SET
LDOK = 0
MODULUS = 3
PWM VALUE = 2
PWMF SET
LDOK = 1
LDOK = 0
MODULUS = 3 _{MODULUS = 3}
PWM VALUE = 2 _{PWM VALUE = 1}
PWMF SET
PWMF SET
LDOK = 0
MODULUS = 3
PWM VALUE = 1
PWMF SET
PWM
Figure 15-7. Edge-Aligned PWM Value Loading
LDFQ1:LDFQ0 = 00 (RELOAD EVERY CYCLE)
UP-ONLY
COUNTER
LDOK = 1
MODULUS = 3
PWM VALUE = 2
PWMF SET
LDOK = 1
MODULUS = 4
PWM VALUE = 2
PWMF SET
LDOK = 1
MODULUS = 2
PWM VALUE = 2
PWMF SET
LDOK = 0
MODULUS = 1
PWM VALUE = 2
PWMF SET
PWM
Figure 15-8. Edge-Aligned Modulus Loading
15.4.2 PWM Data Overflow and Underflow Conditions
The PWM value registers are 16-bit registers. Although the counter is only 12 bits, the user may write a
16-bit signed value to a PWM value register. As shown in Figure 15-4, if the PWM value is less than or
equal to zero, the PWM will be inactive for the entire period. Conversely, if the PWM value is greater than
or equal to the timer modulus, the PWM will be active for the entire period. Refer to
Table 15-3.
MC68HC908LB8 Data Sheet, Rev. 1
148
Freescale Semiconductor