Pulse-Width Modulator (S12PWM8B8CV1)
S12XS Family Reference Manual, Rev. 1.13
390
Freescale Semiconductor
Figure 13-21. PWM Left Aligned Output Example Waveform
13.4.2.6
Center Aligned Outputs
For center aligned output mode selection, set the CAEx bit (CAEx = 1) in the PWMCAE register and the
corresponding PWM output will be center aligned.
The 8-bit counter operates as an up/down counter in this mode and is set to up whenever the counter is
equal to $00. The counter compares to two registers, a duty register and a period register as shown in the
block diagram in
. When the PWM counter matches the duty register, the output flip-flop
changes state, causing the PWM waveform to also change state. A match between the PWM counter and
the period register changes the counter direction from an up-count to a down-count. When the PWM
counter decrements and matches the duty register again, the output flip-flop changes state causing the
PWM output to also change state. When the PWM counter decrements and reaches zero, the counter
direction changes from a down-count back to an up-count and a load from the double buffer period and
duty registers to the associated registers is performed, as described in
Section 13.4.2.3, “PWM Period and
. The counter counts from 0 up to the value in the period register and then back down to 0. Thus the
effective period is PWMPERx*2.
NOTE
Changing the PWM output mode from left aligned to center aligned output
(or vice versa) while channels are operating can cause irregularities in the
PWM output. It is recommended to program the output mode before
enabling the PWM channel.
Figure 13-22. PWM Center Aligned Output Waveform
Period = 400 ns
E = 100 ns
Duty Cycle = 75%
PPOLx = 0
PPOLx = 1
PWMDTYx
PWMDTYx
Period = PWMPERx*2
PWMPERx
PWMPERx
Содержание MC9S12XS128
Страница 4: ...S12XS Family Reference Manual Rev 1 13 4 Freescale Semiconductor ...
Страница 58: ...Device Overview S12XS Family S12XS Family Reference Manual Rev 1 13 58 Freescale Semiconductor ...
Страница 150: ...Memory Mapping Control S12XMMCV4 S12XS Family Reference Manual Rev 1 13 150 Freescale Semiconductor ...
Страница 168: ...Interrupt S12XINTV2 S12XS Family Reference Manual Rev 1 13 168 Freescale Semiconductor ...
Страница 194: ...Background Debug Module S12XBDMV2 S12XS Family Reference Manual Rev 1 13 194 Freescale Semiconductor ...
Страница 364: ...Periodic Interrupt Timer S12PIT24B4CV1 S12XS Family Reference Manual Rev 1 13 364 Freescale Semiconductor ...
Страница 396: ...Pulse Width Modulator S12PWM8B8CV1 S12XS Family Reference Manual Rev 1 13 396 Freescale Semiconductor ...
Страница 506: ...Voltage Regulator S12VREGL3V3V1 S12XS Family Reference Manual Rev 1 13 506 Freescale Semiconductor ...
Страница 736: ...Ordering Information S12XS Family Reference Manual Rev 1 13 736 Freescale Semiconductor ...
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