MC68HC08AZ60CFU MOTOROLA [Motorola, Inc], MC68HC08AZ60CFU Datasheet - Page 251

• Manufacturer Part Number: MC68HC08AZ60CFU
• Description: Advance Information
• Manufacturer: MOTOROLA [Motorola, Inc]

Unbuffered PWM
Signal Generation
9-timb
MOTOROLA
The value in the TIMB counter modulo registers and the selected
prescaler output determines the frequency of the PWM output. The
frequency of an 8-bit PWM signal is variable in 256 increments. Writing
$00FF (255) to the TIMB counter modulo registers produces a PWM
period of 256 times the internal bus clock period if the prescaler select
value is $000 (see TIMB Status and Control Register).
The value in the TIMB channel registers determines the pulse width of
the PWM output. The pulse width of an 8-bit PWM signal is variable in
256 increments. Writing $0080 (128) to the TIMB channel registers
produces a duty cycle of 128/256 or 50%.
Any output compare channel can generate unbuffered PWM pulses as
described in
are unbuffered because changing the pulse width requires writing the
new pulse width value over the value currently in the TIMB channel
registers.
An unsynchronized write to the TIMB channel registers to change a
pulse width value could cause incorrect operation for up to two PWM
periods. For example, writing a new value before the counter reaches
the old value but after the counter reaches the new value prevents any
compare during that PWM period. Also, using a TIMB overflow interrupt
routine to write a new, smaller pulse width value may cause the compare
to be missed. The TIMB may pass the new value before it is written to
the TIMB channel registers.
PTEx/TCHx
Freescale Semiconductor, Inc.
For More Information On This Product,
OVERFLOW
Timer Interface Module B (TIMB)
Go to: www.freescale.com
Pulse Width Modulation (PWM)
Figure 3. PWM Period and Pulse Width
PULSE
WIDTH
PERIOD
COMPARE
OUTPUT
OVERFLOW
COMPARE
Timer Interface Module B (TIMB)
OUTPUT
on page 250. The pulses
MC68HC08AZ60 — Rev 1.0
OVERFLOW
Functional Description
COMPARE
OUTPUT
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