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NUC240-LC2C Datasheet(Fiches technique) 71 Page - Nuvoton Technology Corporation
Numéro de pièce
NUVOTON [Nuvoton Technology Corporation]
Aug 31, 2015
Page 71 of 107
PWM Generator and Capture Timer (PWM)
NUC100 series has 2 sets of PWM groups supporting a total of 4 sets of PWM
generators that can be configured as 8 independent PWM outputs, PWM0~PWM7, or as 4
complementary PWM pairs, (PWM0, PWM1), (PWM2, PWM3), (PWM4, PWM5) and (PWM6,
PWM7) with 4 programmable Dead-zone generators.
Each PWM generator has one 8-bit prescaler, one clock divider with 5 divided frequencies (1, 1/2,
1/4, 1/8, 1/16), two PWM Timers including two clock selectors, two 16-bit PWM counters for PWM
period control, two 16-bit comparators for PWM duty control and one Dead-zone generator. The 4
sets of PWM generators provide eight independent PWM interrupt flags set by hardware when the
corresponding PWM period down counter reaches 0. Each PWM interrupt source with its
corresponding enable bit can cause CPU to request PWM interrupt. The PWM generators can be
configured as one-shot mode to produce only one PWM cycle signal or auto-reload mode to
output PWM waveform continuously.
When PCR.DZEN01 is set, PWM0 and PWM1 perform complementary PWM paired function; the
paired PWM period, duty and Dead-time are determined by PWM0 timer and Dead-zone
generator 0. Similarly, the complementary PWM pairs of (PWM2, PWM3), (PWM4, PWM5) and
(PWM6, PWM7) are controlled by PWM2, PWM4 and PWM6 timers and Dead-zone generator 2,
4 and 6, respectively.
To prevent PWM driving output pin with unsteady waveform, the 16-bit period down counter and
counter/comparator buffer registers the updated value will be load into the 16-bit down counter/
comparator at the time down counter reaching 0. The double buffering feature avoids glitch at
When the 16-bit period down counter reaches 0, the interrupt request is generated. If PWM-timer
is set as auto-reload mode, when the down counter reaches 0, it is reloaded with PWM Counter
Register (CNRx) automatically then start decreasing, repeatedly. If the PWM-timer is set as one-
shot mode, the down counter will stop and generate one interrupt request when it reaches 0.
The value of PWM counter comparator is used for pulse high width modulation. The counter
control logic changes the output to high level when down-counter value matches the value of
The alternate feature of the PWM-timer is digital input Capture function. If Capture function is
enabled the PWM output pin is switched as capture input mode. The Capture0 and PWM0 share
one timer which is included in PWM0 and the Capture1 and PWM1 share PWM1 timer, and etc.
Therefore user must setup the PWM-timer before enable Capture feature. After capture feature is
enabled, the capture always latched PWM-counter to Capture Rising Latch Register (CRLR)
when input channel has a rising transition and latched PWM-counter to Capture Falling Latch
Register (CFLR) when input channel has a falling transition. Capture channel 0 interrupt is
CCR0.CFL_IE0] (Falling latch Interrupt enable) to decide the condition of interrupt occur.
Capture channel 1 has the same feature by setting CCR0.CRL_IE1 and CCR0.CFL_IE1.
And capture channel 2 to channel 3 on each group have the same feature by setting the
corresponding control bits in CCR2. For each group, whenever Capture issues Interrupt 0/1/2/3,
the PWM counter 0/1/2/3 will be reload at this moment.
The maximum captured frequency that PWM can capture is confined by the capture interrupt
latency. When capture interrupt occurred, software will do at least three steps, including: Read
PIIR to get interrupt source and Read CRLRx/CFLRx(x=0~3) to get capture value and finally write
1 to clear PIIR to 0
. If interrupt latency will take time T0 to finish, the capture signal mustn’t
transition during this interval (T0). In this case, the maximum capture frequency will be 1/T0. For
HCLK = 50 MHz, PWM_CLK = 25 MHz, Interrupt latency is 900 ns
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