STR720 datasheet(324/401 Pages) STMICROELECTRONICS

Teilenummer	STR720

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

PDF	401 Pages

Scroll/Zoom	100%

Hersteller	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

Logo

324 / 401 page

STR720 - EXTENDED FUNCTION TIMER (EFT)

324/401

21.3.8

Pulse Width Modulation Input

The PWM Input functionality enables the measurement of the period and the pulse width of an

external waveform. The initial edge is programmable.

It uses the two Input Capture registers and the Input signal of the Input Capture A module.

21.3.8.1 Procedure

The CR2 register must be programmed as needed for Interrupts and DMAs. To use pulse

width modulation mode select the following in the CR1 register:

– set the PWMI bit

– Select the first edge in IEDGA

– Select the second edge IEDGB as the negated of IEDGA

– Program the clock source and prescaler as needed

– Enable the counter setting the EN bit.

To have a coherent measure the interrupt/DMA should be linked to the Input Capture A

Interrupt, reading in ICAR the period value and in ICBR the pulse width.

To obtain the time values:

Where:

fAPB

= APB clock frequency

tPRESC

= Timer clock prescaler: (CC7..CC0)+1

The Input Capture A event causes the counter to be initialized to 0000h, allowing a new

measure to start. The first Input Capture on ICAPA do not generate the corresponding

interrupt request.

Period =

ICAR * fAPB

tPRESC

Pulse =

ICBR * fAPB

tPRESC

STR720 Datenblatt(PDF) 324 Page - STMicroelectronics