STLED325 datasheet(21/62 Pages) STMICROELECTRONICS

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STLED325

Functional description

Doc ID 17576 Rev 1

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WDFEn = watchdog flag enable

12/24 = 12 hour or 24 hour format (‘0’ for 24-hour format and ‘1’ for 12-hour format). For 12

hour PM display, the 8th segment of last digit (digit 4) is driven to indicate PM mode through

a dot on the last digit.

It is recommended to fill the unused bits in the register map to 0 upon a cold boot up. The

timekeepers and alarm store data in BCD format, while the calibration, watchdog bits are in

binary format.

The structure of the frame is shown below. For RTC, all the Dig1 to Dig4 must be configured

to show the proper time.

Figure 8.

Keyscan and digit mapping

If the date programmed in the RTC exceeds a valid date value, then the RTC does not

function as desired. So the invalid dates should never be programmed into the RTC.

3.11.4

Setting alarm clock registers

Address locations 0Ah-0Eh contain the alarm settings. The alarm can be configured to go

off at a prescribed time on a specific month, date, hour, minute, or second or repeat every

year, month, day, hour, minute, or second. It can also be programmed to go off while the

STLED325 is in the standby mode to serve as a system wake-up call.

Bits RPT6-RPT1 put the alarm in the repeat mode of operation. Codes not listed in the table

default to the once per second mode to quickly alert the user of an incorrect alarm setting.

Note that by default, the alarm repeat mode is enabled and by default the repeat frequency

is set to “once per year”.

Address locations 0Ah to 0Eh contain the alarm settings. The alarm can be configured to go

off at a prescribed time. The default repeat alarm mode is once per year. Programming the

RPT[6:1] bits changes the repeat alarm mode.

AM08722V1

Keyscan

Digit 5

(used for

discrete LED)

Dig 1

Dig 2

Dig 3

Dig 4

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