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21.3 Functional description
Timer/Counter control
The PWM has Start/Stop register. It controls start or stop of the Timer/Counter. If you set this
register, the Timer/Counter starts to run. If you reset this register, the Timer/Counter stops
immediately. Also there is a pause register. The pause register is used to stop temporarily after
one period. Although you set this register while the Timer/Counter is running, the
Timer/Counter will stop when the period ends.
The registers of PWM can be updated when it stops or pauses. Users cannot update the
registers while PWM is running.
Timer/Counter
The PWM has 8 Timer/Counter clocks, which can be divided by a prescaler. Each Timer/Counter
runs independently. The Timer/Counter is designed to count cycles of the clocks or external
input signal and generate interrupts when specified timer values are occurred based on match
register and limit register. The Timer/Counter can count up or down.
The PWM has match registers and limit registers. The match registers control the duty cycle
of PWM output waveform. The limit registers control the period of the PWM output waveform.
The Timer/Counter becomes 0 when it reaches value of the limit register. If PDMR(Periodic
Mode Register) is set, the Timer/Counter counts stops counting and if PDMR is reset, the
Timer/Counter counts repeatedly.
Match register should be smaller than limit register(LR). If not, match interrupt is not occurred
and PWM output waveform is always 1.
Repetition mode
The Timer/Counter has two repetition mode: periodic and one-shot mode. In periodic mode,
the Timer/Counter recycles and then restarts when the Timer/Counter reaches the value of
limit register. Figure 23 shows periodic mode timing diagram.
PWMCLK
Prescale
1
2
Counter
Timer/Counter
10
Overflow
Interrupt
W7500x Reference Manual Version1.1.0
Figure 22 PWM block diagram
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