HMP9701A Intersil Corporation, HMP9701A Datasheet - Page 7

• Manufacturer Part Number: HMP9701A
• Description: AC97 Audio Codec
• Manufacturer: Intersil Corporation

AC Link Powerdown
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.
NOTE: BCLK not to scale.
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 1 s 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
1 s. 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”.
SYNC
BCLK
SDATA_OUT
SDATA_IN
PREVIOUS FRAME
FIGURE 7. AC-LINK POWERDOWN TIMING
SLOT 12
SLOT 12
TAG
TAG
TO 26H
WRITE
PR4 = 1
DATA
HMP9701A
7
NORMAL
Suggested Powerdown Sequences
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.
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.
NORMAL
FIGURE 8. EXAMPLE OF SEQUENTIAL POWERDOWN
PR0=1
ADC=1
PR0=0
AND
PR0=1
ADC=1
PR0=0
AND
CODEC
READY
ADCs
OFF
PR0
=1
ADCs
PR1=1
OFF
PR0
DAC=1
PR1=0
AND
PR1=1
DAC=1
PR1=0
AND
DACs
OFF
PR1
DEFAULT
PR2=1
ANL=1
PR2=0
DACs
AND
OFF
PR1
ANALOG
OFF PR2
OR PR3
PR4=1
PR4=1
AC LINK
RESET
WARM
OFF
PR4
AC LINK
RESET
RESET
COLD
WARM
OFF
PR4
POWER
DOWN
POWER
DOWN