Semiconductor

Features

· Fully Compatible with the Audio Codec `97 Standard

· High Fidelity 16-Bit

Converters

- DAC SNR > 80dB

- ADC SNR > 80dB

· Additional A/D for Microphone Pass-Through

· AC Link Serial Interface Compatible with AC'97 Digital

Controllers

· Fixed 48kHz Sampling Rate

· 6 Channel Input Mixer

· Programmable Powerdown Modes

· 48 Lead TQFP Package

· Single +5V Supply

Applications

· Multimedia PC Applications

- Desk Top PCs

- Notebook PCs

- Sound Cards

- Motherboards

· Video Conferencing

· Speaker Phones

Table of Contents

Page

Functional Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Serial Digital Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Control Register Description . . . . . . . . . . . . . . . . . . . . . . . . 8

Pinout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Pin Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

AC and DC Electrical Specifications . . . . . . . . . . . . . . . . . 13

Typical Performance Curves

ADC/DAC Frequency Responses . . . . . . . . . . . . . . . . . 17

AC Timing Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Schematic Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Description

The HMP9701 is the next generation PC based audio codec
solution. The HMP9701 is fully compatible to the new AC'97
standard and, as such, interfaces to any AC'97 compliant digital
controller. The HMP9701 offers the designer a solution to sat-
isfy the demand for flexibility and improved High Fidelity sound
in a PC environment. As part of the AC'97 PC audio standard
architecture, the HMP9701 helps pave the way for PC'97 com-
pliant desktop, portable and entertainment PCs with a cost
effective high-quality audio solution.

As the analog front end of the AC'97 chipset, the HMP9701
accepts line level audio inputs from seven different sources and
converts the analog audio to 16-bit digital streams of either ste-
reo or mono data. The 48 Kss data is transmitted to the control-
ler via the AC'97 standard five wire interface. The controller
sends digital audio data to the HMP9701 to be converted to
analog stereo or monaural line output using two DACs.

We include an additional ADC to be used for Acoustic Echo
Canceling needed for video conferencing applications. This
ADC has a dedicated microphone input. It has the same high
quality performance as the stereo ADCs. The small 48 lead
TQFP (Thin 1.5mm and 7mm x 7mm footprint Quad Flat Pack-
age) makes it easy to locate the analog codec close to the ana-
log sources. Thus, reducing noise and lowering the cost of
implementation.

Ordering Information

PART NUMBER

TEMP.

RANGE (

PACKAGE

PKG. NO.

HMP9701CN

0 to 70

48 Ld TQFP

Q48.7x7A

HMP9701EVAL2

PCI Bus Evaluation Board (Includes codec)

TQFP is also known as PQFP and MQFP.

November 1998

HMP9701

AC'97 Audio Codec

CAUTION: These devices are sensitive to electrostatic discharge. Users should follow proper IC Handling Procedures.

Harris Corporation 1998

File Number

4287.4

FOR A POSSIBLE SUBSTITUTE PR

ODUCT

call Central Applications 1-800-442-7747

or email: centapp@harris.com

OBSOLETE PR

ODUCT

Functional Block Diagram

Functional Description

The HMP9701 is a full-duplex stereo audio codec compliant to
the AC'97 Codec specification. This component is designed for
use in multimedia and business personal computers. The
codec includes full duplex stereo converters, a mic pass
through ADC, complete on-chip anti-alias filtering, and a 5
channel analog mixer with programmable gain and attenuation.

Analog Inputs

The HMP9701 has 4 stereo inputs (LINE_IN, CD, VIDEO, and
AUX), two microphone level inputs (MIC1 and MIC2), and one
mono line level input (PHONE). A multiplexer is provided to
independently select the right and left record sources from the
analog inputs listed above. In addition, the output stereo mix
(LINE_OUT) or its mono equivalent may also be selected as a
record source. A gain block is available to amplify the MIC
inputs by 20dB to compensate for the difference between line
levels and typical condenser microphone levels.

Besides being fed to the Record Select Mux, all analog
inputs can be mixed (see Analog Mixer) with the stereo out-
put from the Playback DACs. Note: all analog inputs except
PHONE and PC_BEEP can be output on MONO_OUT.

There is a dedicated analog input, PC_BEEP, for the
standard "Beep" signal provided on most PC/Compatible
computers for power on self test and boot audio status
indication. This input is mixed into each channel of the
stereo line outputs.

Record ADCs

The HMP9701 provides 3

ADCs to record one dedicated

microphone input and 2 user selectable analog inputs. The
user selectable analog inputs are routed to the stereo ADCs
via an programmable Input Multiplexer. The multiplexer is
programmed to select the 2 record channels via the Record
Select register (1Ah).

Each of the record channels pass through a programmable
gain block before each ADC. The record gain for each chan-
nel is set individually and ranges from 0dB to 22.5dB in
1.5dB increments (see Record Gain Registers 1Ch and
1Eh). The gain block can also be used to mute each chan-
nel. Note: an additional gain block provides 20dB of gain on
the MIC channel if activated (see MIC Volume register 0Eh).

The HMP9701 uses oversampling

ADCs which only

require a single pole passive filter for anti-alias filtering. The
filter for the left, right and MIC channels is realized by placing
a 1nF capacitor between the AFILT1, AFILT2, and AFILT3
pins and analog ground respectively.

Playback DACs

The HMP9701 uses oversampling single bit

DACs to con-

vert the stereo playback sample to an analog line level output.
The output of the DACs pass through internal reconstruction
filters that do not require any external components.

GAIN

0dB/20dB

MONO

VOL

D/A

LINK INTERF

D/A

MIC1

MIC2

LINE_IN

VIDEO

AUX

PC_BEEP

MONO_OUT

LINE_OUT

SYNC
BIT_CLK
SDATA_OUT
SDATA_IN

RESET

PHONE

G
A
M

GAM

AC'97

CONTROL/CONFIGURATION

(64 REGISTERS)

HMP9701 AC'97 AUDIO CODEC

STEREO SIGNAL PATH

MONO SIGNAL PATH

RECORD

GAIN

MASTER

VOL

A/D

MIC

SEL

MONO

SEL

RECORD SELECT

HMP9701

Analog Mixer

The Analog Mixer generates two outputs, one stereo and
one mono. The stereo output is used to drive LINE_OUT and
is composed of a stereo mix of all analog input sources and
the audio output from the DACs. The mono output drives
MONO_OUT, and it is user selectable as either MIC only or
a mono mix of all the analog and PCM sources except the
PHONE and PC_BEEP inputs.

The inputs to the analog mixer pass through gain/attenu-
ate/mute (GAM) blocks. Each gain block provides volume
control from -34.5dB to +12dB in 1.5dB increments (see
Input Volume Registers 0Ch - 18h). Additionally, the GAM
blocks can be used to mute individual mixer inputs. An addi-
tional gain of 20dB is provided for the selected MIC input.
Note: for best SNR performance, the GAM block for the DAC
output should be used to control PCM analaog volume
rather than digitally attenuating the DAC PCM input to take
advantage of full resolution conversions.

Clocking

The HMP9701 derives it's internal clock from an externally
attached 24.576MHz crystal. The crystal and 2 capacitors
are attached to the XTL_IN and XTL_OUT pins, and it
should be fundamental-mode/parallel resonant with a load
capacitor as specified by the crystal manufacturer (typically
12-30pF).

An external CMOS clock may be connected to XTL_OUT
instead of a crystal. If this external clocking option is used,
XTL_IN should be left floating. Please Note: No capacitors
are used on the crystal pins in this mode. For an example
circuit, refer to the Typical Application Schematic.

The HMP9701 divides the clock source by 2 to derive the
BIT_CLK provided to the companion digital controller. The
digital controller should divide the provided BIT_CLK by 256
to generate the 48kHz SYNC signal used to define the audio
frame transmitted over the serial digital interface (See Serial
Digital Interface Section)

Serial Digital Interface

Audio Data Format

The HMP9701 supports 16-bit 2's complement linear PCM
data for record and playback. The 16-bit 2's complement for-
mat (also called 16-bit signed format) is the standard method
of representing 16-bit digital audio. This format gives 96dB
theoretical dynamic range and is the standard for compact
disk audio players. This format uses the value -32768
(8000h) to represent minimum analog amplitude while
32767 (7FFFh) represents maximum analog amplitude.

Digital Serial Interface (AC Link)

The HMP9701 is linked to an AC'97 digital controller via a 5
pin digital serial interface as shown in Figure 1. This inter-
face, the AC-link, supports bidirectional, fixed rate, serial
data streams. The data transfers are based on a time divi-
sion multiplexed (TDM) protocol that provides for multiple
input and output audio streams together with control and sta-
tus data. The AC-link protocol is based on incoming and out-
going audio frames which are each divided into 12 data slots
as shown in Figure 2. The HMP9701 allocates data slots for
2 PCM playback channels, 2 PCM record channels, codec
control, codec status, and a PCM microphone record chan-
nel. The remaining unused time slots are reserved.

SYNC

BIT_CLK

SDATA_OUT

SDATA_IN

RESET

HMP9701

AC'97

AUDIO

CODEC

FIGURE 1. HMP9701 CONNECTION TO AC'97 CONTROLLER

AC'97

DIGITAL

CONTROLLER

PCM

LEFT

RSRVD

MIC

RSRVD

PCM

RIGHT

STATUS

DATA

TAG

STATUS

ADDR

INCOMING

AUDIO STREAMS

PCM

LEFT

RSRVD

PCM

RIGHT

CMD

DATA

TAG

CMD

ADDR

OUTGOING

AUDIO STREAMS

SYNC

SLOT NO.

TAG

PHASE

DATA PHASE

FIGURE 2. AC LINK BIDIRECTIONAL DATA FRAME

HMP9701

The HMP9701 generates a serial bit clock (BIT_CLK) at
12.288MHz for synchronous data transfers on the AC Link.
Data is output on SDATA_IN by the rising edge of BIT_CLK,
and serial data is sampled on SDATA_OUT by the falling
edge of BIT_CLK. An audio frame transfer is initiated by the
assertion of SYNC for the 16 BIT_CLK's comprising the Tag
Phase of the audio frame. The SYNC signal must be
asserted at a fixed 48kHz rate, and it can be derived by
dividing down the BIT_CLK.

The tag phase is a 16-bit data slot (Slot 0) wherein each bit
is a data valid flag for an associated time slot within the cur-
rent audio frame. A "1" in a given bit position of Slot 0 indi-
cates that the corresponding time slot within the audio frame
contains valid data. If the HMP9701 "tags" a slot invalid, it
will set the data bits comprising that slot to zero.

AC Link Output Frame (SDATA_OUT)

The audio output frame contains data targeted for the
HMP9701's DAC inputs, and control registers. This data is
transmitted in slots 1 through 4 of the audio frame as shown
in Figure 2. The tag slot, Slot 0, is a special reserved time
slot containing 16 bits that tell the AC-link interface circuitry
the validity of the following data slots.

The HMP9701 is synchronized to the beginning of a new
audio output frame when SYNC makes a low to high transi-
tion and is sampled low by the falling edge of BIT_CLK as
shown in Figure 3. On the next rising of BIT_CLK, the AC'97
controller drives SDATA_OUT with the first bit of slot 0 (Valid
Frame bit) which is then sampled by the HMP9701 on the
subsequent falling edge of BCLK. The controller drives the
remaining audio frame bits out on SDATA_OUT with each
rising edge of BCLK, and the HMP9701 samples these bits
on the subsequent falling edge.

The first bit of the output audio frame (Slot 0, bit 15) flags the
validity of the entire audio frame. If the "Valid Frame" bit is a
1, this indicates that the current audio frame contains at
least one time slot of valid data. The HMP9701 monitors the
next 4 bit positions to determine whether the data in the con-

trol and PCM output data slots is valid. The remaining 8 bits
in Slot 0 are ignored as they are associated with reserved
data slots.

The 20-bit data word in each time slot must be transmitted MSB
first. If the data word targeted for a time slot is less than 20 bits,
the data word must be MSB justified in the most significant bits
of the time slot with the unused bits set to zero. For example, an
8 bit audio sample would be transmitted in bits 19-12 of the time
slot with the trailing 12 bits set to zero. The MSB of the audio
sample would map to bit 19 of the time slot. Note: for the play-
back of mono audio streams, the digital controller must send
the same sample to each PCM output channel.

Audio Output Slot 1: Control Address

The bits in Slot 1 are used to access the 16 bit control/status
registers within the HMP9701. The address space allocated
in slot 1 allows up to 64 sixteen bit registers, however, only
the even registers are valid (see Control/Status register sec-
tion for a complete register map). The control registers are
read/writable to provide more robust testability. A read or
write command is initiated by setting the Read/Write bit (Bit
19) in Slot 1. A complete bit map for Slot 1 is given in the
Table 1. Note: control data will only be loaded into the target
registers if Slot 2 (Control Data) is flagged as being valid.

VALID

FRAME

SLOT SLOT

SLOT

"0"

BIT 19

BIT 0 BIT 19

BIT 0

BIT 19

BIT 0

SYNC

SDATA_OUT

BIT_CLK

12.288MHz

81.4ns

TAG PHASE

DATA PHASE

20.8

(48kHz)

TIME SLOT "VALID" BITS

("1" = TIME SLOT CONTAINS VALID DATA)

"1" = FRAME CONTAINS

VALID DATA

SLOT 1

SLOT 2

SLOT 12

FIGURE 3. AC LINK AUDIO OUTPUT FRAME

VALID
FRAME

SLOT 1

SLOT 2

SDATA_OUT

BIT_CLK

PREVIOUS

AUDIO FRAME

HMP9701 SAMPLES

SYNC ASSERTION

HMP9701 SAMPLES
FIRST BIT OF AUDIO OUTPUT

SYNC

FIGURE 4. START OF AUDIO OUTPUT FRAME

HMP9701

Audio Output Slot 2: Control Data

This Slot is used to deliver the 16 bit control data if the cur-
rent control register access is a write operation (Bit 19 of Slot
1 is set to "0"). The bit map for Slot 2 is given in Table 2.

Audio Output Slot 3: PCM Playback Left Channel

This time slot contains the audio sample that will be input to
the left channel DAC. The HMP9701 DAC resolution is 17
Bits. All audio samples of 17 or less bits should be MSB jus-
tified within the 20-bit frame, and the trailing bits should be
set to "0". Audio samples greater than 17 bits will be rounded
to 17 bits.

Audio Output Slot 4: PCM Playback Right Channel

This time slot contains the audio sample that will be input to
the right channel DAC. The HMP9701 DAC resolution is 17
Bits. All audio samples of 17 or less bits should be MSB jus-
tified within the 20-bit frame, and the trailing bits should be
set to "0". Audio samples greater than 17 bits will be rounded
to 17 bits.

Audio Output Slots 5-12: Reserved

Audio output slots 5-12 are reserved for future use and
should be set to "0" for proper operation.

AC Link Input Frame (SDATA_IN)

The audio input frame contains captured audio samples and
codec status for output onto the AC-Link. The codec status
is transmitted in slots 1 and 2, and the 16-bit captured audio

samples are returned in slots 3, 4 and 6 as shown in
Figure 2. As before, the tag slot, Slot 0, is a special reserved
time slot containing 16 bits that tell the AC-link interface cir-
cuitry the validity of the following data slots.

The HMP9701 starts a new audio input frame when SYNC
makes a low to high transition and is sampled low by the falling
edge of BIT_CLK as shown in Figures 5 and 6. On the next ris-
ing edge of BIT_CLK, the HMP9701 drives SDATA_IN with the
first bit of slot 0 (Codec Ready bit). The HMP9701 drives the
remaining audio frame bits out on SDATA_IN with each rising
edge of BIT_CLK. Note: SYNC must be synchronous to
BIT_CLK.

The first bit of an input audio frame (Slot 0, bit 15) indicates
whether the HMP970's AC Link is functional. If the "Codec
Ready" bit is a 0, the HMP9701 is not ready for normal oper-
ation. If the "Codec Ready" bit is "1", the HMP9701 is ready
to perform control and status register transfers. At this point,
it is the responsibility of the digital controller to examine the
Powerdown Control/Status register (see Control Register
Section) to determine the operational state of the codec sub-
sections. The 12 bits following the "Codec Ready" Bit in Slot
0 identify which of the 12 time slots contain valid data.

The HMP9701 outputs each time slots data word MSB first
on SDATA_IN. All non-valid bit positions (for active or inac-
tive time slots) are stuffed with 0's by the HMP9701.

Input Audio Slot 1: Status Address

This slot echoes the index of the control register whose con-
tents are returned in slot 2. The data in this register is the
result of a control register read operation initiated by an Out-
put Audio Frame transfer.

TABLE 1. BIT MAP FOR SLOT 1: CONTROL ADDRESS

BITS

DESCRIPTION

COMMENT

Read/Write

1 = Read, 0 = Write

18:12

Control Register
Index

Identifies the Target Control Register

11:0

Reserved

Set to "0"

TABLE 2. BIT MAP FOR SLOT 2: CONTROL DATA

BITS

DESCRIPTION

COMMENT

19:4

Control Register
Write Data

Set to "0" if Read operation

3:0

Reserved

Set to "0"

TABLE 3. BIT MAP FOR SLOT 3: PCM PLAYBACK LEFT

CHANNEL

BITS

DESCRIPTION

COMMENT

19:0

PCM Audio
Sample for Left
Channel

Set unused bit positions to "0"

TABLE 4. BIT MAP FOR SLOT 4: PCM PLAYBACK RIGHT

CHANNEL

BITS

DESCRIPTION

COMMENT

19:0

PCM Audio
Sample for Right
Channel

Set unused bit positions to "0"

TABLE 5. BIT MAP FOR SLOT 1: STATUS ADDRESS

BITS

DESCRIPTION

COMMENT

Reserved

Stuffed with 0

18:12

Control Register
Index

Echo of Control Register Index for
which data is being returned

11:0

Reserved

Stuffed with 0's

CODEC

READY

SLOT 1

SLOT 2

SDATA_IN

BIT_CLK

PREVIOUS AUDIO FRAME

HMP9701 SAMPLES

SYNC ASSERTION

HMP9701 OUTPUTS
FIRST BIT OF AUDIO INPUT FRAME

SYNC

FIGURE 5. START OF AUDIO INPUT FRAME

HMP9701

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