Crystal CS4231A, Руководство пользователя

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GENERAL INFORMATION
The CDB4231/4248 is designed to provide an
easy platform for evaluating the performance of
the CS4231A, CS4231, or CS4248 Parallel Inter-
fac e, Multimedia Audio Codecs in a PC
environment. This board is not a reference de-
sign, although many aspects of the design should
be incorporated in reference designs. The board
is optimized for performance and ease of modifi-
cation for testing purposes. For those interested
in a reference design, the CRD4231 provides
most of the capabilities of the CDB4231, plus
games support.
Software that operates under the Microsoft Win-
dows

environment is also included with
applets that control all the CS4231 or CS4248
features. This software also provides full Win-
dows

3.1 compatibility with extensions to
utilize the more powerful CS4231 features in
custom code.
Four stereo jacks, externally accessible, allow
connection to Microphone inputs, Auxiliary 1 in-
puts, Line inputs, and Line/Headphone outputs.
Headers allow internal connections to a CD-
R OM an al og out put (usin g t he cod ec’s
Auxiliary 2 inputs), and speaker pass-through
and control via the
SPEAKER IN
(Mono In) and
SPEAKER OUT
(Mono Out) headers.
Additional headers on the board allow the setting
of the Base Address, DMA channel, and IRQ for
th e C S423 1. T he factory default for the
CDB4231 is base address 530h, DMA playback
channel 3, DMA capture channel 0 and IRQ 7.
The CDB4248 is the same with the exception of
the DMA capture header which is not used and
has both shorting jumpers removed.
The software must be configured to match the
settings on the evaluation board headers for
proper operation.
STEREO ANALOG INPUTS
Three of the four external
1
/
8
" stereo jacks are
for analog inputs. The stereo
Mic I
, Microphone
Input, (Figure 2) contains an op-amp buffer with
a gain of 18 dB providing a maximum full scale
input to the evaluation board of 12 mV (with the
20 dB boost inside the codec enabled). For mi-
crophones that output signals larger than 12 mV,
the 20 dB gain block inside the codec can be
disabled in software (the "Boost" button in the
input applet). With the 20 dB gain block dis-
abled, the maximum full-scale value is 120 mV.
The microphone circuit is designed for single-
ended microphones which are the most common
type available. The J35 header, close to the mic
input jack allows selection of a stereo micro-
phone when the jumper is in the ’S’ position, or
mono input where the jumper is in the ’M’ posi-
tion. In the mono position, a mono mic input
would go to both the left and right mic input
pins on the codec.
The second input jack is
Ax1 I
, Auxiliary 1 In,
(Figure 1) which has an input impedance of ap-
proximately 10 k
Ω
with a maximum full scale
into the
Ax1 I
jack of 2 V
RMS
.
The third stereo input jack is
Line I
, Line In,
(Figure 4) which also has a maximum full scale
of 2 V
RMS
and provides a typical audio input
impedance of 47 k
Ω
.
An internal header, labeled
CDROM IN (AUX2),
(Figure 4) may be used by any internal device
for analog mixing into the codec’s output mixer
via the Auxiliary 2 inputs, AUX2. Since the
AUX2 inputs don’t have a path to the ADCs,
when nothing is plugged into the
Line I
jack, the
analog contained on the
CDROM IN
header is
summed into the Line inputs of the codec as
well as the AUX2 inputs. When a plug is in-
serted into the
Line I
jack, the
CDROM IN
header
is disconnected from the Line inputs (but is still
connected to the AUX2 inputs).
CDB4231/4248
58 DS111DB7