PCF2131 datasheet(46/85 Pages) NXP

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NXP Semiconductors

PCF2131

Nano-power highly accurate RTC with integrated quartz crystal

The pulse generator for the minute/second interrupt operates from an internal 64 Hz clock and generates a

pulse of 1⁄64 seconds in duration.

7.13.2 INTA/B pulse shortening

If the MSF flag (register Control_2) is cleared before the end of the INTA/B pulse, then the INTA/B pulse is

shortened. This allows the source of a system interrupt to be cleared immediately when it is serviced, that is, the

system does not have to wait for the completion of the pulse before continuing; see Figure 20. Instructions for

clearing the bit MSF can be found in Section 7.11.5.

aaa-041573

seconds counter

MSF

INTA/B

SCL

instruction

CLEAR INSTRUCTION

8th clock

(1)

1. Indicates normal duration of INTA/B pulse.

The timing shown for clearing bit MSF is also valid for the non-pulsed interrupt mode, that is, when TI_TP is logic 0, where

the INTA/B pulse may be shortened by setting both bits MI and SI logic 0.

Figure 20. Example of shortening the INTA/B pulse by clearing the MSF flag

7.13.3 Watchdog timer interrupts

The generation of interrupts from the watchdog timer is controlled using the WD_CD bit (register

Watchdg_tim_ctl). The interrupt is generated as an active signal which follows the status of the watchdog timer

flag WDTF (register Control_2) if not masked. No pulse generation is possible for watchdog timer interrupts.

The interrupt is cleared when the flag WDTF is reset. Instructions for clearing it can be found in Section 7.11.5.

7.13.4 Alarm interrupts

Generation of interrupts from the alarm function is controlled by the bit AIE (register Control_2). If AIE is

enabled, the INTA/B pin follows the status of bit AF (register Control_2) if not masked. Clearing AF immediately

clears INTA/B. No pulse generation is possible for alarm interrupts.

PCF2131

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Product data sheet

Rev. 2.0 — 5 October 2023

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