WM8351 datasheet(193/330 Pages) WOLFSON

193 / 330 page

Production Data

WM8351

PD, April 2012, Rev 4.5

193

The applicable register bits are defined in Table 135.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R12 (0Ch)

Power

Mgmt (5)

RTC_TICK_ENA

Enable RTC counting (instruction only)

0 = disabled

1 = enabled

Protected by security key.

R218 (DAh)

RTC Tick

Control

RTC_TICKSTS

Status of tick request. This bit can be used

to ensure the RTC is using the value of

RTC_TICK_ENA.

0 = disabled

1 = enabled

Protected by security key.

9:0

RTC_TRIM [9:0]

00_0000_

0000

RTC frequency trim. Used to adjust the

count value of the Tick Gen block to

compensate for crystal inaccuracies.

RTC frequency trim is a 10bit fixed point

<4,6> 2's complement number. MSB

Scaling = -8Hz. The register indicates the

error (in Hz) with respect to the ideal

32768Hz) of the input crystal frequency.

e.g.:

Actual crystal freq: 32769.00Hz:

Required trim 0xb0001_000000

(+1.000000)

Actual crystal freq: 32767.00Hz:

Required trim 0xb1111_000000 (-

1.000000)

Actual crystal freq: 32775.58Hz:

Required trim 0xb0111_100101

(+7.578125)

Actual crystal freq: 32763.78Hz:

Required trim 0xb1011_110010 (-

4.218750)

Protected by security key.

Note:

RTC_TICK_ENA can be accessed through R12 or through R218. Reading from or writing to

either register location has the same effect.

Table 135 Controlling the RTC Frequency Trim

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).

WM8351 Datasheet(PDF) 193 Page - Wolfson Microelectronics plc

WM8351 Datasheet(HTML) 193 Page - Wolfson Microelectronics plc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL