WM8352 datasheet(192/336 Pages) WOLFSON

192 / 336 page

WM8352

Production Data

PD, February 2011, Rev 4.4

192

22.2.5

SETTING THE ALARM

Writing to the RTC Alarm registers requires a procedure similar to that used when setting RTC time,

in order to prevent accidental alarms being triggered:



Set the RTC_ALMSET bit to disable alarms



Read the RTC_ALMSTS bit. Repeat this step until RTC_ALMSTS=1



Set new RTC Alarm in Registers R20 to R22



Clear the RTC_ALMSET bit to re-enable RTC Alarm

The RTC_ALMSET and RTC_ALMSTS bits are defined in Table 134.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R23 (17h)

RTC Time

control

RTC_ALMSET

Stops alarms (instruction only)

0 = normal operation

1 = stop alarms

It is recommended to stop alarms when

setting the RTC alarm. This avoids false

alarms.

RTC_ALMSTS

Actual status of ALARM circuitry

0 = normal operation

1 = alarms stopped

Table 134 Setting the RTC Alarm

22.3 TRIMMING THE RTC

The RTC has a frequency trim feature to allow compensation for known and constant errors in the

crystal oscillator frequency up to ±8Hz. Programming the frequency trim requires a procedure similar

to that used when setting RTC and ALARM time:



Clear the RTC_TICK_ENA bit to disable the 1 second tick generator



Read the RTC_TICKSTS bit. Repeat this step until RTC_TICKSTS=1



Set new RTC frequency trim value in Register R218



Set the RTC_TICK_ENA bit to resume normal operation

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