AD1985

Rev. A | Page 26 of 48

Power-Down Control/Status Register (Index 0x26)

Reg Num

Name

D15

D14 D13 D12 D11 D10 D9

D8

D7 D6 D5 D4 D3

D2

D1

D0

Default

0x26

Power-Down Ctrl/Stat

EAPD PR6

PR5

PR4 PR3 PR2 PR1 PR0 X

X

X

X

REF ANL DAC ADC N/A

Note that the ready bits are read-only; writing to REF, ANL, DAC, and ADC will have no effect. These bits indicate the status for the AD1985 subsections. If the bit is a 1,

then that subsection is ready. Ready is defined as the subsection able to perform in its nominal state.

ADC

ADC Sections Ready to Transmit Data.

DAC

DAC Sections Ready to Accept Data.

ANL

Analog Amplifiers, Attenuators, and Mixers Ready.

REF

PR[6:0]

Codec Power-Down Modes. Some bits can be used individually, while others are used in combination.

PR0

ADCs and Input Mux Power-Down. Default setting is 0.

PR1

DACs Power-Down. Also powers down the EQ circuitry. Default setting is 0.

PR2

Mixer Power-Down. Default setting is 0.

PR3

May be used in combination with PR2 or by itself. If all the ADCs and DACs are not powered down, setting this bit will have no

PR4

AC Link Interface Power-Down. Default setting is 0. The reference and the mixer can be either up or down, but all power-up

sequences must be allowed to run to completion before PR5 and PR4 are both set.

In multiple-codec systems, the master codec’s PR4 bit controls the slave codec. In the slave codec, the PR4 bit has no effect,

except to enable or disable PR5.

PR5

Internal Clocks Disabled. Default setting is 0.

PR5 has no effect, unless all ADCs, DACs, and the AC link are powered down, e.g., PR0, PR1, PR4. The reference and the mixer can

be either up or down, but all power-up sequences must be allowed to run to completion before PR5 and PR4 are both set. In

multiple codec systems, the master codec’s PR5 controls the slave codec. PR5 is effective in the slave codec if the master's PR5 bit

is clear.

PR6

Powers Down the Headphone Amplifiers. Default setting is 0.

EAPD

External Audio Power-Down Control. Controls the state of the EAPD pin.

EAPD = 0 sets the EAPD pin low, enabling an external power amplifier. (Reset default.)

EAPD = 1 sets the EAPD pin high, shutting the external power amplifier off.

NORMAL

ADCs OFF

PR0

DACs OFF

PR1

ANALOG

OFF

PR2 OR

PR3

DIGITAL I/F

OFF

PR4

SHUT OFF

AC-LINK

PR0 = 1

PR1 = 1

PR2 = 1

PR4 = 1

DEFAULT

PR0 = 0

AND

ADC = 1

PR1 = 0

AND

DAC = 1

PR2 = 0

AND

ANL = 1

WARM

RESET

COLD

RESET

READY = 1

Figure 11. Example of AC ’97 Power-Down/Power-Up Flow