ST72321 datasheet(63/189 Pages) STMICROELECTRONICS

Teilenummer	ST72321

Bauteilbeschribung	64/44-PIN 8-BIT MCU WITH 32 TO 60K FLASH/ROM, ADC,FIVE TIMERS, SPI, SCI, I2C INTERFACE

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Hersteller	STMICROELECTRONICS [STMicroelectronics]

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ST72321

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PWM AUTO-RELOAD TIMER (Cont’d)

Output compare and Time base interrupt

On overflow, the OVF flag of the ARTCSR register

is set and an overflow interrupt request is generat-

ed if the overflow interrupt enable bit, OIE, in the

ARTCSR register, is set. The OVF flag must be re-

set by the user software. This interrupt can be

used as a time base in the application.

External clock and event detector mode

Using the fEXT external prescaler input clock, the

auto-reload timer can be used as an external clock

event detector. In this mode, the ARTARR register

is used to select the nEVENT number of events to

be counted before setting the OVF flag.

nEVENT = 256 - ARTARR

Caution: The external clock function is not availa-

ble in HALT mode. If HALT mode is used in the ap-

plication, prior to executing the HALT instruction,

the counter must be disabled by clearing the TCE

bit in the ARTCSR register to avoid spurious coun-

ter increments.

Figure 41. External Event Detector Example (3 counts)

COUNTER

FDh

FEh

FFh

FDh

OVF

ARTCSR READ

INTERRUPT

ARTARR=FDh

fEXT=fCOUNTER

FEh

FFh

FDh

IF OIE=1

INTERRUPT

IF OIE=1

ARTCSR READ

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