WM9705 datasheet(34/55 Pages) WOLFSON

34 / 55 page

WM9705

Production Data

PD Rev 4.0 December 2003

Figure 16 illustrates one example procedure to do a complete Powerdown of the WM9705. From

normal operation sequential writes to the Powerdown Register are performed to Powerdown the

WM9705 a piece at a time. After everything has been shut off (PR0 to PR3 set), a final write (of

PR4) can be executed to shut down the WM9705’s digital interface (AC-link).

The part will remain in sleep mode with all its registers holding their static values. To wake up the

WM9705, the AC’97 controller will send a pulse on the sync line issuing a warm reset. This will

restart the WM9705’s digital interface (resetting PR4 to 0). The WM9705 can also be woken up

with a cold reset. A cold reset will cause a loss of values of the registers, as a cold reset will set

them to their default states. When a section is powered back on, the Powerdown Control/Status

attempting any operation that requires it.

PR0 = 1

PR1 = 1

PR4 = 1

NORMAL

ADC’s OFF

PR0

DIGITAL I/F

OFF PR4

WARM RESET

PR0 = 0 AND

ADC = 1

PR1 = 0 AND

DAC = 1

SHUT OFF

CODA LINK

DACs OFF

PR1

Figure 17 The WM9705 Powerdown Flow with Analogue Still Active

Figure

17 illustrates a state when all the mixers should work with the static volume settings that

are contained in their associated registers. This is used when the user could be playing a CD (or

external LINEIN source) through WM9705 to the speakers but have most of the system in low

power mode. The procedure for this follows the previous except that the analogue mixer is never

shut down.

The device can be used as a pen digitiser only, in order to set the WM9705 into this mode

powerdown bits PR3 to 0, PR6 and EAPD should be set.

Note that in order to go into ultimate low power mode, PR4 and PR5 are required to be set which

turns off the oscillator circuit. Asserting SYNC resets the PR4 and PR5 bit and re-starts the

oscillator in the same way as the AC link is restarted.

The Extended Audio ID register is a read only register that identifies which extended audio

features are supported (in addition to the original AC’97 features identified by reading the reset

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