• EPWM signal between 0% and 100% if CNTIN < CnV <=
MOD,
• 100% EPWM signal when CNTIN > CnV or CnV > MOD.
41.5.8 Center-Aligned PWM (CPWM) mode
The Center-Aligned mode is selected when:
• QUADEN = 0
• DECAPEN = 0
• COMBINE = 0, and
• CPWMS = 1
The CPWM pulse width (duty cycle) is determined by 2 × (CnV − CNTIN) and the
period is determined by 2 × (MOD − CNTIN). See the following figure. MOD must be
kept in the range of 0x0001 to 0x7FFF because values outside this range can produce
ambiguous results.
In the CPWM mode, the FTM counter counts up until it reaches MOD and then counts
down until it reaches CNTIN.
The CHF bit is set and channel (n) interrupt is generated (if CHIE = 1) at the channel (n)
match (FTM counter = CnV) when the FTM counting is down (at the begin of the pulse
width) and when the FTM counting is up (at the end of the pulse width).
This type of PWM signal is called center-aligned because the pulse width centers for all
channels are aligned with the value of CNTIN.
The other channel modes are not compatible with the up-down counter (CPWMS = 1).
Therefore, all FTM channels must be used in CPWM mode when (CPWMS = 1).
pulse width
counter overflow
FTM counter =
MOD
period
2 x (CnV - CNTIN)
2 x (MOD - CNTINCNTIN)
FTM counter = CNTIN
channel (n) match
(FTM counting
is down)
channel (n) match
(FTM counting
is up)
counter overflow
FTM counter =
MOD
channel (n) output
Figure 41-21. CPWM period and pulse width with ELSB:ELSA = 1:0
Functional description
Kinetis KE1xF Sub-Family Reference Manual, Rev. 4, 06/2019
1038
NXP Semiconductors
Содержание KE1xF Series
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