PCF85263ATSLASHA datasheet(26/100 Pages) NXP

26 / 100 page

PCF85263A

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Product data sheet

Rev. 4.1 — 27 November 2015

26 of 100

NXP Semiconductors

PCF85263A

Tiny RTC with alarm, battery switch-over, and I2C-bus

The assertion of flags A1F or A2F can be used to generate an interrupt at the pins INTA

and INTB. The interrupt may be generated as a pulse signal every time the time

increments to match the alarm setting or as a permanently active signal which follows the

condition of bit A1F and/or A2F. See Section 8.9 on page 38 for interrupt control.

A1F and A2F remain set until cleared by command. Once an alarm flag has been cleared,

it will only be set again when the time increments to match the alarm condition once more.

When an interrupt pin is configured to pulse mode and if an alarm flag is not cleared and

the time increments to match the alarm condition again, then a repeated interrupt pulse

will be generated.

8.5 WatchDog

[1]

Default value.

8.5.1 WatchDog functions

The WatchDog has four selectable step sizes allowing for periods in the range from

62.5 ms to 124 seconds. For periods greater than 2 minutes, the alarm function can be

used.

(1)

[1]

Time periods can be affected by correction pulses.

Table 17.

WatchDog - WatchDog control and register (address 2Dh) bit description

Bit

Symbol

Value

Description

7WDM

WatchDog mode

0[1]

single shot

repeat mode

6 to 2

WDR[4:0]

WatchDog register bits

0h[1] to 1Fh

Write: WatchDog counter load value

0h to 1Fh

Read: current counter value

1 to 0

WDS[1:0]

WatchDog step size (source clock)

00[1]

4 seconds (0.25 Hz)

1 second (1 Hz)

1⁄4 second (4 Hz)

1⁄16 second (16 Hz)

Table 18.

WatchDog durations

WDS[1:0] WatchDog step

size[1]

Delay

Minimum WatchDog duration

WDR = 1

Maximum WatchDog duration

WDR = 31

4 s

124 s

1 s

31 s

1⁄4 s

0.25 s

7.75 s

1⁄16 s

0.0625 s

1.9375 s

WatchDog-duration

WDR

stepsize



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