WM9708

Advanced Information

WOLFSON MICROELECTRONICS LTD

AI Rev 2.0 April 2001

22

POWERDOWN CONTROL/STATUS REGISTER (INDEX 26h)

This read/write register is used to program Powerdown states and monitor subsystem readiness. The

lower half of this register is read only status, a 1 indicating that the subsection is ready. Ready is

defined as the subsection able to perform in its nominal state. When this register is written the bit

values that come in on AC-link will have no effect on read only bits 0 to 7.

When the AC-link Codec Ready indicator bit (SDATAIN slot 0, bit 15) is a 1 it indicates that the AC-

link and the WM9708 control and status registers are in a fully operational state. The AC’97 controller

must further probe this Powerdown Control/Status Register to determine exactly which subsections, if

any, are ready.

READ BIT

FUNCTION

REF

VREFs up to nominal level

ANL

Analogue mixers, etc ready

DAC

DAC section ready to accept data

ADC

ADC section ready to transmit data

Table 10 Powerdown Status Register Function

The powerdown modes are as follows. The first three bits are to be used individually rather than in

combination with each other. The last bit PR3 can be used in combination with PR2 or by itself. PR0

and PR1 control the PCM ADCs and DACs only. PR6 is not supported by the WM9708.

WRITE BIT

FUNCTION

PR0

PCM in ADCs and input Mux Powerdown

PR1

PCM out DACs Powerdown

PR2

Analogue mixer Powerdown

(VREF still on)

PR3

Analogue mixer Powerdown (VREF off)

PR4

Digital interface (AC-link) Powerdown

(external clock off)

PR5

Internal clock disable

PR6

HP amp Powerdown – not supported

EAPD

External amplifier Powerdown

Table 11 Powerdown Control Register Function

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 WM9708 Powerdown/Powerup Flow

Figure 13 illustrates one example procedure to do a complete Powerdown of the WM9708. From

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

WM9708 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 WM9708’s digital interface (AC-link).