pwm unit 17 로봇 sw 교육원 조용수. 학습 목표 pwm pwm register 2

PWMUNIT

17

로봇 SW 교육원조용수

2학습 목표

• PWM• PWM Register

3PWM

• Pulse Width Modulation• 진폭이 일정한 상태에서 펄스 폭을 증 / 감 하여

신호를 변화시키는 방법• 디지털 출력으로 아날로그 회로를 제어할 수 있음 .• Duty Cycle : High Level 과 Low Level 간의 비율

4

N051 PWM

• Four PWM Generators, each generator supports• One 8-bit prescaler • One clock divider ( 1, ½, ¼, 1/8, 1/16)• Two PWM-timers for two outputs, each timer includes

• A 16-bit PWM down-counter• A 16-bit PWM reload value register (CNR)• A 16-bit PWM compare register (CMR)

• One dead-zone generator• Two PWM outputs.

• 8 PWM channels or 4 PWM paired channels.• 16 bits resolution.• Support edge and center aligned modes• Single-shot or Continuous mode PWM.

PWM/Capture Clock Source

5

6

PWM Edge Align Mode

• Duty ratio = (CMR+1) / (CNR+1)• Duty = (CMR+1) x (clock period)• Period = (CNR+1) x (clock period)

+

-

CMRn+1

CNRn

PWM-TimerComparator

Output CNRn

CMRn

Update new CMRn

StartInitialize

PWM

PWMOuput

CMRn+1CNRn+1

7

PWM Double Buffering Illustration

PWM Waveform

write a nonzero number to prescaler & setup clock dividor

Start

CNR=150 CMR=50

151

51

200

50

CNR=199 CMR=49

CNR=99 CMR=0

100

1

CNR=0 CMR=XX

Stop

New period (CNR)New duty (CMR)

S/W write new period (CNR)And new duty (CMR)

First cycle Second cy-cle

8

Operation of Dead Zone Generator • Why need the dead zone control?

– To avoid a paired-PWM outputs overlapping on duty-on du-ration.

– For example, in Motor Driver application, it needs to avoid the upper and lower power switch turn on simultaneously.

• Insert a delay time (dead zone) before duty on at each channel of paired-PWM.

• 8-bit dead-zone timer from PWM clock.

PG0 withoutdead-zone

PG1 withoutdead-zone

PWM0 withdead-zone

PWM1 withdead-zone

Dead-zone Interval

Effect of dead-zone for complementary pairs

pwm unit 17 로봇 sw 교육원 조용수. 학습 목표 pwm pwm register 2

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