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

9PWM Register

10PWM Register

11PWM Register

12PWM Register

13PWM Register

14PWM Register

15PWM Register

16PWM Register

17PWM Register

18PWM Register

19PWM Register

20PWM Register

21PWM Register

22PWM Register

23PWM Register

24PWM Register

25PWM Register

26PWM Register

27PWM Register