M41TC8025 datasheet(8/41 Pages) STMICROELECTRONICS

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Operation

M41TC8025

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DocID022873 Rev 4

Operation

2.1

Overview of functions

2.1.1

User interface

The M41TC8025 RTC operates as a slave device on the serial I2C bus. Access is obtained

by implementing a START condition followed by the correct slave address (64h, see Table 3

on page 11). The 16-byte registers contained in the device can then be accessed.

2.1.2

Temperature-compensated clock and calendar

The M41TC8025 RTC provides the date and time (seconds, minutes, hours, day of week,

date (day of month), month and year) while incorporating temperature compensation

(sampling period user-programmable) to maintain accurate timekeeping over the extended

temperature range of -45 to +70 °C or the industrial temperature range of -40 to +85 °C.

Leap year is compensated automatically. Refer to Section 2.4: Clock and calendar on

page 15.

2.1.3

Programmable clock output

The M41TC8025 RTC provides a programmable, accurate 1 Hz, 1,024 Hz (1 KHz) and

32,768 Hz (32 KHz) output on the FOUT pin. The FOUT pin is a CMOS output and is

controlled by the FOE pin.

If the FOE pin is logic high, the FOUT output is enabled. If the FOE pin is logic low, the

FOUT output is disabled and is Hi-Z. Refer to Section 2.5: Programmable frequency output

on FOUT pin on page 17 for a detailed description.

2.1.4

Fixed-cycle timer interrupt

The fixed-cycle timer interrupt function generates periodic interrupts at any fixed-cycle

programmed between 244.14 μs and 4095 minutes.

When an interrupt is generated, the IRQ pin will be pulled low if enabled (bit TIE=1) and the

flag bit (TF) will be set to 1 to indicate the interrupt occurrence. After the IRQ pin is pulled

low, it will be automatically released (change to Hi-Z) after time tRTN so that periodic

interrupts can be generated even though the user does not clear the flag bit (no auto-clear

of the flag bit). Refer to Section 2.6: Fixed-cycle timer interrupt on page 18 for a detailed

description.

2.1.5

Time update interrupt

The time update interrupt function generates periodic interrupts at one-second or one-

minute cycles based on the internal clock timing update.

When a time update is generated, the IRQ pin will be pulled low if enabled (bit UIE=1) and

the flag bit (UF) will be set to 1 to indicate the time update occurrence. After the IRQ pin is

pulled low, it will be automatically released (change to Hi-Z) after time tRTN so that periodic

interrupts can be generated even if the user does not clear the flag bit (no auto-clear of the

flag bit). Refer to Section 2.7: Time update interrupt function on page 22 for a detailed

description.

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