Pulse-Width Modulator (S12PWM8B8CV2)
MC9S12G Family Reference Manual Rev.1.27
648 NXP Semiconductors
Clock Source = E, where E = 10 MHz (100 ns period)
PPOLx = 0
PWMPERx = 4
PWMDTYx = 1
PWMx Frequency = 10 MHz/8 = 1.25 MHz
PWMx Period = 800 ns
PWMx Duty Cycle = 3/4 *100% = 75%
Shown in Figure 19-20 is the output waveform generated.
Figure 19-20. PWM Center Aligned Output Example Waveform
19.4.2.7 PWM 16-Bit Functions
The scalable PWM timer also has the option of generating up to 8-channels of 8-bits or 4-channels of
16-bits for greater PWM resolution. This 16-bit channel option is achieved through the concatenation of
two 8-bit channels.
The PWMCTL register contains four control bits, each of which is used to concatenate a pair of PWM
channels into one 16-bit channel. Channels 6 and 7 are concatenated with the CON67 bit, channels 4 and
5 are concatenated with the CON45 bit, channels 2 and 3 are concatenated with the CON23 bit, and
channels 0 and 1 are concatenated with the CON01 bit.
NOTE
Change these bits only when both corresponding channels are disabled.
When channels 6 and 7 are concatenated, channel 6 registers become the high order bytes of the double
byte channel, as shown in Figure 19-21. Similarly, when channels 4 and 5 are concatenated, channel 4
registers become the high order bytes of the double byte channel. When channels 2 and 3 are concatenated,
channel 2 registers become the high order bytes of the double byte channel. When channels 0 and 1 are
concatenated, channel 0 registers become the high order bytes of the double byte channel.
When using the 16-bit concatenated mode, the clock source is determined by the low order 8-bit channel
clock select control bits. That is channel 7 when channels 6 and 7 are concatenated, channel 5 when
channels 4 and 5 are concatenated, channel 3 when channels 2 and 3 are concatenated, and channel 1 when
channels 0 and 1 are concatenated. The resulting PWM is output to the pins of the corresponding low order
8-bit channel as also shown in Figure 19-21. The polarity of the resulting PWM output is controlled by the
PPOLx bit of the corresponding low order 8-bit channel as well.
E = 100 ns
DUTY CYCLE = 75%
E = 100 ns
PERIOD = 800 ns
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