HMP9701A 데이터 시트보기 (PDF) - Intersil
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HMP9701A Datasheet PDF : 20 Pages
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HMP9701A
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 analog volume rather
than digitally attenuating the DAC PCM input to take advan-
tage of full resolution conversions.
Clocking
The HMP9701A 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). For an example circuit, refer to the Typical Appli-
cation Schematic.
An external CMOS clock may be connected to XTL_IN
instead of a crystal. If this external clocking option is used,
XTL_OUT should be left floating. Please Note: No capaci-
tors are used on the crystal pins in this mode.
The HMP9701A 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 HMP9701A 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.
AC’97
DIGITAL
CONTROLLER
SYNC
BIT_CLK
SDATA_OUT
SDATA_IN
RESET
HMP9701A
AC’97
AUDIO
CODEC
FIGURE 1. HMP9701A CONNECTION TO AC’97 CONTROLLER
Digital Serial Interface (AC Link)
The HMP9701A 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 HMP9701A allocates data slots
for 2 PCM playback channels, 2 PCM record channels,
codec control, codec status, and a PCM microphone record
channel. The remaining unused time slots are reserved.
SLOT NO.
SYNC
0
1
2
3
4
5
6
7
8
9
10
11
12
OUTGOING
AUDIO STREAMS
TAG
CMD CMD
ADDR DATA
PCM PCM
LEFT RIGHT RSRVD RSRVD RSRVD RSRVD RSRVD RSRVD RSRVD RSRVD
INCOMING
AUDIO STREAMS
TAG
STATUS STATUS
ADDR DATA
PCM
LEFT
PCM
RIGHT RSRVD
MIC
RSRVD RSRVD RSRVD RSRVD RSRVD RSRVD
TAG
PHASE
DATA PHASE
FIGURE 2. AC LINK BIDIRECTIONAL DATA FRAME
3
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