WM8351CGEB/RV WOLFSON [Wolfson Microelectronics plc], WM8351CGEB/RV Datasheet - Page 192

• Manufacturer Part Number: WM8351CGEB/RV
• Manufacturer: WOLFSON [Wolfson Microelectronics plc]

WM8351
22.3 TRIMMING THE RTC
w
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:
R23 (17h)
RTC Time
control
Table 134 Setting the RTC Alarm
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:
22.2.5
The RTC_ALMSET and RTC_ALMSTS bits are defined in Table 134.
ADDRESS








SETTING THE ALARM
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
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
BIT
9
8
RTC_ALMSET
RTC_ALMSTS
LABEL
DEFAULT
1
1
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.
Actual status of ALARM circuitry
0 = normal operation
1 = alarms stopped
DESCRIPTION
PD, April 2012, Rev 4.5
Production Data
192