UM1539 datasheet(28/46 Pages) STMICROELECTRONICS

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Getting started

UM1539

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Doc ID 023106 Rev 1

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.

1.2.30

M41T83_QFN 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 read flags, 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

1.2.31

M41T83_QFN RTC timer configuration

M41T83 RTC has an 8-bit countdown timer. This timer counts down from the user

configured value to 1 and then again reloads the timer countdown value.

Enter any value between 1 and 255 inside the value area of the timer.

Select the timer ticking clock from the clock frequency dropdown menu of the timer.

Enable the checkbox for the TE bit, this enables the timer. If the TE bit is not enabled,

the timer does not start the counting. The TI/TP checkbox selects the mode of the

timer.

The TIE bit is used to output the timer rollover interrupt on the #IRQ1 interrupt pin of

RTC. Whenever the timer rollover occurs, the TF flag is set and the D6 LED glows on

the motherboard. The LED goes off by reading the flag register using Read Flag button.

Press the Write button to enter the timer configuration values in the timer section of

M41T83_QFN RTC.

As soon as the timer rolls over from 1 to the timer countdown value, the timer flag (TF)

is set inside the flag status register of RTC. This flag is cleared only by reading the flag

second read clears the flag from the GUI.

1.2.32

M41T83_QFN RTC digital calibration configuration

Enter the calibration value between 0-31 in the calibration register.

Select the positive or negative calibration by selecting the sign in the sign bit dropdown

menu.

Press the Write button to configure the RTC calibration register with the selected

settings.

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