PCF2123U datasheet(11/54 Pages) NXP

Part #	PCF2123U

Description	SPI Real time clock/calendar

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Manufacturer	NXP [NXP Semiconductors]

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11 / 54 page

PCF2123_1

Product data sheet

Rev. 01 — 19 November 2008

11 of 54

NXP Semiconductors

PCF2123

SPI Real time clock/calendar

9.3.2 Register Control_2

9.4 OS ﬂag

The PCF2123 includes a ﬂag (bit OS) which is set whenever the oscillator is stopped (see

Figure 8 and Figure 9). The ﬂag will remain set until cleared by software. If the ﬂag cannot

be cleared, then the PCF2123 oscillator is not running. This method can be used to

monitor the oscillator and to determine if the supply voltage has reduced to the point

where oscillation fails.

Table 6.

Register Control_2 (address 01h) bits description

Bit

Symbol

Value

Description

Reference

7

MI

0

minute interrupt is disabled

Section 9.8.1

1

minute interrupt is enabled

6

SI

0

second interrupt is disabled

1

second interrupt is enabled

5

MSF

0

no minute or second interrupt generated

1

ﬂag set when minute or second interrupt

generated;

ﬂag must be cleared to clear interrupt

when TI_IP = 0

4

TI_TP

0

interrupt pin follows timer ﬂags

Section 9.9.2

1

interrupt pin generates a pulse

3

AF

0

no alarm interrupt generated

Section 9.7.1

1

ﬂag set when alarm triggered;

ﬂag must be cleared to clear interrupt

2

TF

0

no countdown timer interrupt generated

-

1

ﬂag set when countdown timer interrupt

generated;

ﬂag must be cleared to clear interrupt

when TI_IP = 0

1

AIE

0

no interrupt generated from the alarm ﬂag

Section 9.9.3

1

interrupt generated when alarm ﬂag set

0

TIE

0

no interrupt generated from the countdown

timer

Section 9.9.2

1

interrupt generated by the countdown timer

Fig 8.

OS set by failing VDD

001aai561

VDD

VOSC(MIN)

t

battery operation

main supply

Similar Part No. - PCF2123U

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NXP Semiconductors	PCF2123	844Kb / 63P	SPI Real time clock/calendar Time keeping application Rev. 5-27 April 2011
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PCF2123U Datasheet(PDF) 11 Page - NXP Semiconductors

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