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2014-07-02 - Tiny Gecko Family - d0034_Rev1.20
262
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Figure 17.17. TIMER Up-count Frequency Generation
0
TIMERn_TOP
TIMERn_CCx _CCV
The output frequency is given by Equation 17.2 (p. 262)
TIMER Up-count Frequency Generation Equation
f
FRG
= f
HFPERCLK
/ ( 2^(PRESC + 1) x (TOP + 1) x 2)
(17.2)
17.3.2.5 Pulse-Width Modulation (PWM)
In PWM mode, TIMERn_CCx_CCV is buffered to avoid glitches in the output. The settings in the
Compare Output Action configuration bits are ignored in PWM mode and PWM generation is only
supported for up-count and up/down-count mode.
17.3.2.6 Up-count (Single-slope) PWM
If the counter is set to up-count and the Compare/Capture channel is put in PWM mode, single slope
PWM output will be generated (see Figure 17.18 (p. 262) ). In up-count mode the PWM period is TOP
+1 cycles and the PWM output will be high for a number of cycles equal to TIMERn_CCx_CCV. This
means that a constant high output is achieved by setting TIMER_CCx to TOP+1 or higher. The PWM
resolution (in bits) is then given by Equation 17.3 (p. 262) .
Figure 17.18. TIMER Up-count PWM Generation
0
TIMERn_TOP
TIMERn_CCx _CCV
TIMn_CCx
Overflow
Com pare m at ch
Buffer updat e
TIMER Up-count PWM Resolution Equation
R
PWM
up
= log(TOP+1)/log(2)
(17.3)
The PWM frequency is given by Equation 17.4 (p. 262) :
TIMER Up-count PWM Frequency Equation
f
PWM
up/down
= f
HFPERCLK
/ ( 2^PRESC x (TOP + 1)
(17.4)
The high duty cycle is given by Equation 17.5 (p. 263)
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