wm8350 Wolfson Microelectronics plc, wm8350 Datasheet - Page 193

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

Production Data
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The current time can be read from the registers defined above. As the content of the time registers
changes every second, a single register read, executed at an arbitrary time, does not guarantee an
accurate time reading. Two possible methods are recommended for reliable reading of the time
registers:
22.2.3
When writing to the RTC time registers, the seconds counter should first be stopped in order to
prevent glitches. The following procedure should be used:
The RTC_SET and RTC_STS bits are defined in Table 131.
R23 (17h)
RTC Time
control
Table 131 Setting the RTC Time
22.2.4
An RTC Alarm can be set by writing to the control fields in registers R20 to R22, which are in a
similar format to the RTC Time registers.
Setting any of these fields to “All 1’s” results in that field being a “don’t care” field. For example,
setting the RTC_ALMDAY field to 0001 determines that the alarm is set for a Sunday, whilst setting
RTC_ALMDAY to 1111 results in the programmed alarm occurring on every day of the week.
When the RTC Alarm time/date fields match the RTC time, the alarm event is signalled by the
WM8350 raising the RTC_ALM_EINT interrupt. See Section 22.5 for further details.
ADDRESS






RTC ALARM REGISTERS
Read after interrupt: the RTC_SEC interrupt (see Section 22.5) indicates that the seconds
counter has just been incremented, and that the RTC registers will not change again within
the next 999ms. A register read executed immediately after an RTC_SEC interrupt can
therefore be taken as an accurate time reading.
Two consecutive reads: if two consecutive reads within a short time (less than 1s apart)
return the same result, this can be taken as an accurate reading. If the two results differ,
the procedure should be repeated.
SETTING THE TIME
Set the RTC_SET bit to stop seconds counter
Read the RTC_STS bit. Repeat this step until RTC_STS=1
Set new time in Registers R16 to R19
Clear the RTC_SET bit to re-enable seconds counter.
BIT
11
10
RTC_SET
RTC_STS
LABEL
DEFAULT
0
0
Stops RTC seconds counter (instruction only)
0 = normal operation
1 = stop counter
Status of RTC seconds counter
0 = normal operation
1 = counter stopped
DESCRIPTION
PD, June 2009, Rev 4.1
WM8350
193