UM1539 datasheet(31/46 Pages) STMICROELECTRONICS

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UM1539

Getting started

Doc ID 023106 Rev 1

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1.2.39

M41T83_SOX18 RTC alarm settings

M41T83_SOX18 RTC has two alarm functions:

●

Alarm one

●

Alarm two

Alarm one:

Set the alarm date and time using the alarm one date and time section on the RTC GUI

window.

Check the A1IE checkbox to see the alarm status on the interrupt output pin of RTC.

This is seen as a D6 LED glowing on the motherboard whenever the alarm match

occurs.

Press the Write button to program the alarm one date and time in the RTC.

As the Alarm time is matched, the AF1 flag sets inside the flag status register and if

A1IE is also checked, the D6 LED glows on the motherboard. This alarm can be seen

in the GUI by pressing the Read Flag button, the AF1 flag glows and is cleared on a

second press of read flags.

D6 LED shows the status of the #IRQ1 pin of the RTC.

Alarm two:

Set the alarm date and time using the alarm two date and time section on the RTC GUI

window.

Check the AL2E bit to enable the alarm two function. The A2IE bit is used to enable the

alarm match status output on the #IRQ2 pin of RTC.

Press the Write button to program the alarm two configuration in RTC.

On the matching of RTC clock date and time with the alarm two date and time, the AF2

flag is set inside the flag status register and, if the A2IE bit is checked, then the alarm

match status is also seen on the motherboard as the glow of D1 LED. D1 LED goes off

on pressing the Read Alarm button.

The alarm status can be seen in the GUI by pressing the Read Flags button. Pressing

read flags again clears the alarm register of RTC and its new status is shown in the

GUI.

The Reset OF button is used to reset the OF bit in the alarm register and,

correspondingly, the oscillator bit alarm is also cleared by the Reset button.

1.2.40

M41T83_SOX18 RTC watchdog configuration

The watchdog of RTC is enabled by configuring the multiplier and resolution settings

and pressing the Write button.

The time period for watchdog is calculated by the resolution x multiplier value. This

value is in seconds.

The watchdog alarm occurs when the time set in the watchdog register has lapsed.

The status of the watchdog alarm can be seen only by pressing the Read Flags button

and, on the motherboard, this status is shown by the glow of the D6 LED. Pressing

again the Read Alarm button clears the WDG flag in the alarm register of RTC and its

status is shown in the GUI. On the motherboard the D6 LED goes off only by writing the

watchdog register. Writing 0 in the watchdog register disables the watchdog function.

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