WM8352
Production Data
22.4 RTC GPIO OUTPUT
It is possible to configure GPIO6 as an RTC output, as described in Section 20. This output is a
square wave that is derived from the trimmed RTC counter. The frequency can be set to values
between 1Hz and 16.384kHz, as described in Table 136.
Note that, when RTC_TRIM is used to calibrate the crystal oscillator, the nominal 50% duty ratio of
this output may deviate by up to 8 clock periods of the 32.768kHz oscillator on the occasions when
the RTC Seconds Counter is increased (ie. once per second).
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
Divided Square wave select.
0000 = disabled
0001 = 1Hz
R23 (17h)
3:0
RTC_DSW [3:0]
0000
RTC Time
control
0010 = 2Hz
…
1011 = 1024Hz
1100 = 2048Hz
1101 = 4096Hz
1110 = 8192Hz
1111 = 16384Hz
Note: due to trim settings for crystal
intolerances a single square wave period
during seconds rollover may be decrease
its on time period or increase its off time
period by up to 8 32kHz periods.
Table 136 RTC GPIO Output
PD, February 2011, Rev 4.4
194
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
