PC87413 datasheet(157/257 Pages) NSC

157 / 257 page

8.0 Real-Time Clock (RTC) (Continued)

Revision 1.2

157

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8.3.15

RTC Control Register C (CRC)

Power Well:VPP

Location: Index 0Ch

Type:

8.3.16

RTC Control Register D (CRD)

Power Well: VPP

Location: Index 0Dh

Type:

Bit

76543210

Name

IRQF

PIF

Reserved

Reset

00000000

Bit

Description

IRQF (IRQ Flag). This bit mirrors the value on the interrupt output signal. When interrupt is active, this bit is 1.

To clear this bit (and deactivate the interrupt pin), perform a read on the CRC register. This read also clears ﬂag

bits UF, AF and PF.

0: IRQ inactive

1: IRQ active, according to the equation: ((UIE and UF) or (AIE and AF) or (PIE and PF)); see Section 8.3.14 on

page 156

PIF (Periodic Interrupt Flag). This bit is cleared to 0 on RTC reset (i.e., hardware or software reset) or when

the RTC is disabled. In addition, this bit is cleared to 0 when this register is read.

0: No transition occurred on the selected tap since the last read

1: Transition occurred on the selected tap of the divider chain

AIF (Alarm Interrupt Flag). This bit is cleared to 0 as long as bit 7 of the CRD register is reads 0. In addition,

this bit is cleared to 0 when this register is read.

0: No alarm detected since the last read

1: Alarm condition detected

UIF (Update Ended Interrupt Flag). This bit is cleared to 0 on RTC reset (i.e., hardware or software reset) or

the RTC disabled. In addition, this bit is cleared to 0 when this register is read.

0: No update occurred since the last read

1: Time registers updated

3-0

Reserved.

Bit

76543210

Name

Valid RAM

and Time

Reserved

Reset

00000000

Bit

Description

Valid RAM and Time. This bit senses the voltage that feeds the RTC (VSB or VBAT) and indicates if the voltage

dropped below the speciﬁed minimum value VBATMIN. If the voltage is too low, the RTC contents (time/calendar

registers and CMOS RAM) are not valid. Reading this bit enables its updating by the status of the RTC supply

voltage.

0: RTC contents not valid

1: RTC contents (time/calendar registers and CMOS RAM) are valid

6-0

Reserved.

PC87413 데이터시트(PDF) 157 Page - National Semiconductor (TI)

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