PCF2123TS datasheet(10/55 Pages) NXP

10 / 55 page

PCF2123_2

Product data sheet

Rev. 02 — 4 December 2009

10 of 55

NXP Semiconductors

PCF2123

SPI Real time clock/calendar

9.3.2 Register Control_2

[1]

Default value.

9.4 OS ﬂag

The PCF2123 includes a ﬂag (OS in register Seconds, see Table 8) 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.

Control_2 - control and status register 2 (address 01h) bits description

Bit

Symbol

Value

Description

Reference

7MI

0[1]

minute interrupt is disabled

Section 9.8.3

minute interrupt is enabled

6SI

0[1]

second interrupt is disabled

second interrupt is enabled

MSF

0[1]

no minute or second interrupt generated

ﬂag set when minute or second interrupt

generated;

ﬂag must be cleared to clear interrupt

when TI_IP = 0

TI_TP

0[1]

interrupt pin follows timer ﬂags

Section 9.9.2

interrupt pin generates a pulse

3AF

0[1]

no alarm interrupt generated

Section 9.7.5

ﬂag set when alarm triggered;

ﬂag must be cleared to clear interrupt

2TF

0[1]

no countdown timer interrupt generated

Section 9.8.4

ﬂag set when countdown timer interrupt

generated;

ﬂag must be cleared to clear interrupt

when TI_IP = 0

AIE

0[1]

no interrupt generated from the alarm ﬂag

Section 9.9.3

interrupt generated when alarm ﬂag set

TIE

0[1]

no interrupt generated from the countdown

timer

Section 9.9.2

interrupt generated by the countdown timer

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