WM9704M

Production Data

WOLFSON MICROELECTRONICS LTD

PD Rev 3.2 January 2001

28

PR0 = 1

PR1 = 1

PR2 = 1

PR4 = 1

PR0 = 0 AND

ADC = 1

DEFAULT

READY = 1

COLD RESET

WARM

RESET

PR2 = 0 AND

ANL = 1

PR1 = 0 AND

DAC = 1

ADCs OFF

PR0

DACs OFF

PR1

ANALOGUE

OFF PR2 OR

PR3

DIGITAL I/F

OFF PR4

SHUT OFF

CODA LINK

NORMAL

Figure 13 An Example of the WM9704M Powerdown/Powerup Flow

Figure 13 illustrates one example procedure to do a complete powerdown of the WM9704M. From

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

WM9704M 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 WM9704M’s digital interface (AC-link).

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

WM9704M, the AC’97 controller will send a pulse on the sync line issuing a warm reset. This will

restart the WM9704M’s digital interface (resetting PR4 to 0). The WM9704M 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 register

(index 26h) should be read to verify that the section is ready (i.e. stable) before attempting any

operation that requires it.

Alternatively if RESETB is held low, all PR bits are held set so the device is held powered off until

RESETB is taken high again.

PR1 = 1

PR2 = 1

PR4 = 1

ADCs OFF

PR0

DACs OFF

PR1

ANALOGUE

OFF PR2 OR

PR3

DIGITAL I/F

OFF PR4

WARM RESET

PR1 = 0

AND

DAC = 1

PR2 = 0 AND

ANL = 1

SHUT OFF

CODA LINK

Figure 14 The WM9704M Powerdown/Flow with Analogue Still Alive

Figure 14 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

LINE_IN source) through WM9704M 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.