M058SFAN Datasheet, PDF (43/72 Pages) List of Unclassifed Manufacturers – 32-bit Microcontroller

NuMicro M058S Series Datasheet
6.7 PWM Generator and Capture Timer (PWM)
6.7.1 Overview
The NuMicro^TM M058S has one sets of PWM groups supporting a total of two sets of PWM
generators, which can be configured as four independent PWM outputs, PWM0~PWM3, or as two
complementary PWM pairs, (PWM0, PWM1) and (PWM2, PWM3) with 2 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 2
sets of PWM generators provide four independent PWM period interrupt flags set by hardware
when the corresponding PWM period down counter reaches 0. Each PWM period 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 DZEN01 (PCR[4]) is set, PWM0 and PWM1 perform complementary PWM paired function;
the paired PWM period, duty and Dead-zone are determined by PWM0 timer and Dead-zone
generator 0. Similarly, the complementary PWM pairs of (PWM2, PWM3) are controlled by PWM2
timers and Dead-zone generator 2. Refer to figures below for the architecture of PWM Timers.
To prevent PWM driving output pin with unsteady waveform, the 16-bit period down counter and
16-bit comparator are implemented with double buffer. When user writes data to
counter/comparator buffer registers, the updated value will be loaded into the 16-bit down
counter/ comparator at the time down counter reaching 0. The double buffering feature avoids
glitch at PWM outputs.
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 and then starts 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
compare register.
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 set the PWM-Timer before enabling the 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
programmable by setting CRL_IE0 (CCR0[1]) (Rising latch Interrupt enable) and CFL_IE0
(CCR0[2]) (Falling latch Interrupt enable) to decide the condition of interrupt occur. Capture
channel 1 has the same feature by setting CRL_IE1 (CCR0[17]) and CFL_IE1 (CCR0[18]). The
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
Nov. 27, 2014
Page 43 of 72
Rev.1.03