HMP9701A Просмотр технического описания (PDF) - Intersil

Номер в каталоге

Компоненты Описание

производитель

HMP9701A

AC’97 Audio Codec

Intersil 

HMP9701A

AC Link Powerdown

Suggested Powerdown Sequences

The AC-link interface can be placed in a low power mode by

setting PR4 = 1 in the Powerdown Register (see above). In

this mode, both BIT_CLK and SDATA_IN are forced to a

logic “low” voltage level.

SYNC

PR0=1

PR1=1

PR2=1

PR4=1

NORMAL

ADCs

OFF

PR0

DACs

OFF

PR1

ANALOG

OFF PR2

OR PR3

AC LINK

OFF

PR4

POWER

DOWN

BCLK

SDATA_OUT SLOT 12 TAG

SDATA_IN SLOT 12 TAG

WRITE

TO 26H

DATA

PR4 = 1

PR0=0

AND

ADC=1

PR1=0

AND

DAC=1

PR2=0

AND

ANL=1

CODEC

READY

=1

DEFAULT

WARM

RESET

COLD

RESET

PREVIOUS FRAME

NOTE: BCLK not to scale.

FIGURE 7. AC-LINK POWERDOWN TIMING

As shown in Figure 7 BIT_CLK and SDATA_IN are driven

low immediately following the decode of the write to the Pow-

erdown Control/Status Register (26h) with PR4 = 1. Once

HMP9701A has been instructed to powerdown the AC Link,

a special “wake up” sequence is required to return the AC-

Link to active mode. Note: any valid slots of audio output

samples in the frame containing the AC Link powerdown

command will be dropped.

Waking up the AC-Link

There are 2 methods for bringing the HMP9701A’s AC-link out

of powerdown mode. The first is a “warm reset” that preserves

reactivates the AC Link while preserving the contents of the

HMP9701A control registers. The second is a “Cold Reset”

that reactivates the digital interface while resetting the control

registers to their default values. Once the AC Link has been

powered up, its operational readiness will be indicated via the

Codec Ready bit in the audio input frame (slot 0, bit 15).

Warm AC Link Reset

A warm reset will reactivate the HMP9701A’s AC-link without

altering the current control register values. A warm reset is

generated by driving SYNC high for a minimum of 1µs in the

absence of BIT_CLK. Within normal audio frames SYNC is a

synchronous BIT_CLK. However, in the absence of BIT_CLK,

SYNC functions as an asynchronous input that is used to gen-

erate a warm reset. The activation of BIT_CLK will not occur

until after the falling edge (high to low transition) of the “wake

up” SYNC. Note: the HMP9701A will not respond to a “warm

reset” via the SYNC input for 4 audio frame times following the

frame that triggered the powerdown.

Cold AC Link Reset

A cold reset is achieved by asserting RESET for a minimum of

1µs. By driving RESET low, BIT_CLK will be activated, the

AC-Link will return to normal operation, and all HMP9701A

control registers will be initialized to their default values.

RESET is an asynchronous HMP9701A input. Note: the

HMP9701A will remain in the reset state as long as RESET is

asserted “low”.

FIGURE 8. EXAMPLE OF SEQUENTIAL POWERDOWN

Figure 8 illustrates the complete powerdown of the

HMP9701A. Starting from normal operation, sequential

writes to the Powerdown Register are performed to power-

down one codec section at a time. After powering down the

converters and the analog front end, a final write to PR4 is

executed to shut down the HMP9701A’s digital interface

(AC-link). The part will remain in sleep mode with all its reg-

isters holding their static values.

A warm reset can be used to wake up the AC link which can

then be used to sequentially power up each codec section.

Each section should be powered up sequentially, and the

Powerdown Control/Status register (26h) should be read to

verify that a powered up section is stable/ready before pre-

ceding to power up the next section as shown in Figures 8

and 9. Note: after a complete powerdown, care must be taken

to make sure the Analog Mixer (PR2, PR3) is powered up and

stable before preceding to power up the ADCs and DACs.

PR0=1

PR1=1

PR4=1

NORMAL

ADCs

OFF

PR0

DACs

OFF

PR1

PR0=0

AND

ADC=1

PR1=0

AND

DAC=1

AC LINK

OFF

PR4

WARM

RESET

POWER

DOWN

FIGURE 9. HMP9701A POWERDOWN/UP WITH ANALOG ALIVE

The Figure 9 illustrates an HMP9701A powerdown

sequence that will keep all the mixers operational with the

static volume settings contained in their associated registers.

This powerdown scenario could be used to place the

HMP9701A in low power mode while preserving the capabil-

ity to play a CD (or external LINE_IN source) through the

HMP9701A to the speakers.

7

Share Link: