mc68hc908jb8 Freescale Semiconductor, Inc, mc68hc908jb8 Datasheet - Page 183

• Manufacturer Part Number: mc68hc908jb8
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

11.5.3.2 Buffered Output Compare
11.5.4 Pulse Width Modulation (PWM)
MC68HC908JB8•MC68HC08JB8•MC68HC08JT8 — Rev. 2.3
Freescale Semiconductor
NOTE:
Channels 0 and 1 can be linked to form a buffered output compare
channel whose output appears on the PTE1/TCH0 pin. The TIM channel
registers of the linked pair alternately control the output.
Setting the MS0B bit in TIM channel 0 status and control register (TSC0)
links channel 0 and channel 1. The output compare value in the TIM
channel 0 registers initially controls the output on the PTE1/TCH0 pin.
Writing to the TIM channel 1 registers enables the TIM channel 1
registers to synchronously control the output after the TIM overflows. At
each subsequent overflow, the TIM channel registers (0 or 1) that control
the output are the ones written to last. TSC0 controls and monitors the
buffered output compare function, and TIM channel 1 status and control
register (TSC1) is unused. While the MS0B bit is set, the channel 1 pin,
PTE2/TCH1, is available as a general-purpose I/O pin.
In buffered output compare operation, do not write new output compare
values to the currently active channel registers. User software should
track the currently active channel to prevent writing a new value to the
active channel. Writing to the active channel registers is the same as
generating unbuffered output compares.
By using the toggle-on-overflow feature with an output compare channel,
the TIM can generate a PWM signal. The value in the TIM counter
modulo registers determines the period of the PWM signal. The channel
pin toggles when the counter reaches the value in the TIM counter
modulo registers. The time between overflows is the period of the PWM
signal.
As
registers determines the pulse width of the PWM signal. The time
between overflow and output compare is the pulse width. Program the
TIM to clear the channel pin on output compare if the state of the PWM
pulse is logic 1. Program the TIM to set the pin if the state of the PWM
pulse is logic 0.
Figure 11-3
Timer Interface Module (TIM)
shows, the output compare value in the TIM channel
Timer Interface Module (TIM)
Functional Description
Technical Data
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