ST10R272L - PWM MODULE
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10.1.2 Mode 1 - symmetrical PWM generation (center aligned)
Mode 1 is selected by setting bit PM3 in register PWMCON1 to ‘1’. In this mode, the PWM
timer PT3 is counts up until it reaches the value in the period register PP3. On the next count
pulse, the count direction is reversed and the timer starts counting down with subsequent
count pulses until it reaches the value 0000h. On the next count pulse, the count direction is
reversed again and the count cycle is repeated with the following count pulses.
The PWM output signal is switched to a high level when the timer contents are equal to or
greater than the contents of the pulse width shadow register while the timer is counting up.
The signal is switched back to a low level when the respective timer has counted down to a
value below the contents of the pulse width shadow register. So in mode 1, the value of PW3
register controls both edges of the output signal.
Note that in this mode, the period of the PWM signal is twice the period of the timer:
PWM
Period Mode 1
= 2 * ([PP3] + 1)
Figure 66 illustrates the operation and output waveforms of the PWM channel in Mode 1 for
different values in the pulse width register PW3. This mode is referred to as Center Aligned
