C167CS Datasheet, PDF (346/517 Pages) Infineon Technologies AG – 16-Bit Single-Chip Microcontroller

C167CS
Derivatives
The Pulse Width Modulation Module
Mode 1: Symmetrical PWM Generation (Center Aligned PWM)
Mode 1 is selected by setting the respective bit PMx in register PWMCON1 to ‘1’. In this
mode the timer PTx of the respective PWM channel is counting up until it reaches the
value in the associated period shadow register. Upon the next count pulse the count
direction is reversed and the timer starts counting down now with subsequent count
pulses until it reaches the value 0000_H. Upon 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 this
PWM value controls both edges of the output signal.
Note that in mode 1 the period of the PWM signal is twice the period of the timer:
PWM_Period_Mode1 = 2 × ([PPx] + 1)
Figure 17-4 illustrates the operation and output waveforms of a PWM channel in mode 1
for different values in the pulse width register. This mode is referred to as Center Aligned
PWM, because the value in the pulse width (shadow) register effects both edges of the
output signal symmetrically.
User’s Manual
17-5
V2.0, 2000-07