STR720 datasheet(154/401 Pages) STMICROELECTRONICS

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STR720 - REAL TIME CLOCK (RTC)

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Bit 2 = PERIR: PERiodic Interrupt Request

This bit stores the status of periodic interrupt request signal (RTC_PerIT) generated by the

20 bit programmable counter when the threshold set in RTCP register is reached. When this

bit is at ‘1’, the corresponding interrupt will be generated only if PEREN bit is set to ‘1’. PERIR

bit can be set at ‘1’ only by hardware and can be cleared only by software, while writing ‘1’ will

left it unchanged.

0: Periodic interrupt condition not met.

1: Periodic interrupt request pending.

Bit 1 = AIR: Alarm Interrupt Request

This bit contains the status of periodic interrupt request signal (RTC_AlarmIT) generated by

the 48 bit programmable counter when the threshold set in RTCA register is reached. When

this bit is at ‘1’, the corresponding interrupt will be generated only if AEN bit is set to ‘1’. AIR bit

can be set at ‘1’ only by hardware and can be cleared only by software, while writing ‘1’ will left

it unchanged.

0: Alarm interrupt condition not met.

1: Alarm interrupt request pending.

Note

The alarm event generated during the standby mode (and so with the device kept

under Reset by external RSTIN forced low) does not set the AIR bit.

Note

Any alarm event generated during STOP mode occurs after 1s regardless of the

value programmed in the RTCA register.

Bit 0 = Reserved. This bits must always be written to ‘0’, but it will be read back as ‘1’.

Any interrupt request remains pending until the appropriate RTCCR request bit is reset by

software, notifying that the interrupt request has been granted.

RTCCNT: RTC Counter registers

The RTC counter has three 16 bit programmable counters; their count rate is based on the

CLK_AF time reference. RTCCNT registers keep the counting value of these counters. They

are write protected by bit RTOFF of RTCCR register, write operation is allowed if RTOFF

value is ‘1’. A write operation on any of the three registers (CNT_H, CNT_M or CNT_L) loads

directly the corresponding programmable counter. When reading, the current value in the

counter (system date) is returned. The counters keep on running while the external clock

oscillator is working even if the system is powered down.

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