NXP Semiconductors KE1xF Series, Reference Manual, Page: 1107 / 1483

0x16 0x1B 0x00 0x05 0x0A 0x0F 0x14 0x19 0x1E 0x03 0x08 0x0D 0x12 0x17 0x1C 0x01 0x06 0x0B 0x10 0x15 0x1A 0x1F 0x04 0x09 0x0E 0x13 0x18 0x1D 0x02 0x07 0x0C 0x11 0x16 0x1B 0x00 0x05
PWM period T1 =
(MOD - CNTIN + 1) x T
PWM period T2 =
(MOD - CNTIN + 1 + 1) x T
T1
one unit of
FTM counter
accumulator
overflow
32 x PWM periods
T2 T2 T2 T2
T2
6 x T1
6 x T1 5 x T1
5 x T1
5 x T1
PWM period
dithering
channel (n) output
channel (n) output
channel (n) is in EPWM
CNTIN = 0x0000
MOD = 0x0063
FRACMOD = 0x05
PS[2:0] = 3'b000
T is the period of one unit of FTM counter
Thus, the values (in decimal) are:
T1 = 100 x T
T2 = 101 x T
average period = (100 + 5/32) x T = 100.15625 x T
PWM period
dithering
PWM period
dithering
PWM period
dithering
PWM period
dithering
PWM period
dithering
Figure 41-103. Example of Average Period when the PWM Period Dithering is used with
the Up Counting
NOTE
For the generation of 100% PWM signal in the channel (n)
(with channel (n) ELSB:ELSA = 2'b10) using EPWM mode
and PWM Period Dithering, it is recommended to use (C(n) >
MOD + 1).
For the generation of PWM signals in the channel (n) (with
channel (n) ELSB:ELSA = 2'b10) using Combine mode and
PWM Period Dithering, it is recommended to use:
• For 0% PWM signal: (C(n)V > MOD + 1) and (C(n+1)V >
MOD + 1);
• For 100% PWM signal: (C(n)V = CNTIN) and (C(n+1)V >
MOD + 1).
41.5.33.1.2 Up-Down Counting
When the FTM counter is an up-down counter and the PWM period dithering is enabled,
at the end of each PWM period, the FRACMOD value is added to an internal 5-bit
accumulator. When this accumulator overflows (that is, the result of the adding is greater
or equal than 0x20), then one unit of FTM counter is added to the end of the current
PWM period and other unit is added to the begin of the next PWM period (see the figure
below). After the accumulator overflows, the accumulator remains with the rest of the
subtraction: (the result of this adding - 0x20).
Due to one unit of FTM counter that can be added to the PWM period, the largest valid
value for MOD is 0x7FFE for PWM period dithering in up-down counting (CPWM
mode).
Chapter 41 FlexTimer Module (FTM)
Kinetis KE1xF Sub-Family Reference Manual, Rev. 4, 06/2019
NXP Semiconductors 1107