STR720 datasheet(312/401 Pages) STMICROELECTRONICS

Part #	STR720

Description	ARM720T 16/32-BIT MCU WITH 16K RAM, USB, CAN, 3 TIMERS, ADC, 6 COMMUNICATIONS INTERFACES

PDF	401 Pages

Scroll/Zoom	100%

Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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312 / 401 page

STR720 - EXTENDED FUNCTION TIMER (EFT)

312/401

21.3.2

External Clock

The external clock (where available) is selected if ECKEN = 1 in CR1 register.

The status of the EXEDG bit determines the type of level transition on the external clock pin

EXTCLK that will trigger the counter.

The counter is synchronized with the rising edge of the internal clock coming from the APB

block.

At least four rising edges of the APB_CLK must occur between two consecutive active edges

of the external clock; thus the external clock frequency must be less than a quarter of the APB

clock frequency.

Figure 44. Counter Timing Diagram, internal clock divided by 2

Figure 45. Counter Timing Diagram, internal clock divided by 4

APB_CLK

FFFD FFFE FFFF 0000

0001

0002

0003

INTERNAL RESET

TIMER STROBE:

COUNTER REGISTER

OVERFLOW FLAG TOF

FFFC

FFFD

0000

0001

APB_CLK

INTERNAL RESET

TIMER STROBE

COUNTER REGISTER

OVERFLOW FLAG TOF

STR720 Datasheet(PDF) 312 Page - STMicroelectronics