wm8350 Wolfson Microelectronics plc, wm8350 Datasheet - Page 195

• Manufacturer Part Number: wm8350
• Description: Wolfson Audioplus? Stereo Codec With Power Management
• Manufacturer: Wolfson Microelectronics plc

Production Data
22.3 TRIMMING THE RTC
w
22.2.5
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:
The RTC_ALMSET and RTC_ALMSTS bits are defined in Table 133.
R23 (17h)
RTC Time
control
Table 133 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:
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
0
0
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, June 2009, Rev 4.1
WM8350
195