Добавил:
Upload Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз: Предмет: Файл:
Скачиваний:
83
Добавлен:
01.03.2016
Размер:
3.56 Mб
Скачать

16-bit advanced control timer (TIM1)

RM0016

 

 

17.4.4External clock source mode 2

The counter can count at each rising or falling edge on the ETR. This mode is selected by writing ECE = 1 in the TIM1_ETR register.

The Figure 47 gives an overview of the external trigger input block.

Figure 47. External trigger input block diagram

 

 

 

 

 

 

 

 

 

 

or

TI2F

or

encoder

 

 

 

 

 

 

 

TI1F

or

 

 

 

 

 

 

 

 

 

mode

 

 

 

 

 

 

 

 

TRGI

 

external clock

 

ETR

 

 

 

 

 

 

mode 1

CK_PSC

ETR pin

0

 

ETRP

 

ETRF

 

 

 

 

 

divider

filter

 

external clock

 

 

 

 

 

 

 

fMASTER

 

 

mode 2

 

 

 

 

/1, /2, /4, /8

down-counter

 

 

 

 

 

1

 

 

 

 

 

 

 

 

 

 

fMASTER

internal clock

 

 

 

 

 

 

 

 

ETP

ETPS[1:0]

 

ETF[3:0]

(internal clock) mode

 

 

 

 

 

 

 

 

 

 

 

TIM1_ETR

TIM1_ETR

 

TIM1_ETR

 

 

ECE

SMS[2:0]

 

 

 

 

 

 

 

 

TIM1_ETR

 

TIM1_SMCR

Procedure

 

 

 

 

 

 

 

 

 

 

Use the following procedure to configure the up-counter and, for example, to count once every two rising edges on the ETR:

1.As no filter is needed in this example, write ETF[3:0] = 0000 in the TIM1_ETR register.

2.Set the prescaler by writing ETPS[1:0] = 01 in the TIM1_ETR register.

3.Select rising edge detection on the ETR pin by writing ETP = 0 in the TIM1_ETR register.

4.Enable external clock mode 2 by writing ECE = 1 in the TIM1_ETR register.

5.Enable the counter by writing CEN = 1 in the TIM1_CR1 register.

The counter counts once every two ETR rising edges.

The delay between the rising edge on the ETR and the actual reset of the counter is due to the resynchronization circuit on the external trigger signal (ETRP).

Figure 48. Control circuit in external clock mode 2

fMASTER

 

 

 

CNT_EN

 

 

 

ETR

 

 

 

ETRP

 

 

 

ETRF

 

 

 

COUNTER CLOCK = CK_CNT = CK_PSC

 

 

 

COUNTER REGISTER

34

35

36

152/454

Doc ID 14587 Rev 9

Соседние файлы в папке Минимум документации STM8