adav400kstz-reel Analog Devices, Inc., adav400kstz-reel Datasheet - Page 18

• Manufacturer Part Number: adav400kstz-reel
• Description: Audio Codec With Embedded Sigmadsp Processor
• Manufacturer: Analog Devices, Inc.

ADAV400
SIGNAL PROCESSING
The ADAV400 is designed to provide all the signal processing
functions commonly used in stereo or multichannel playback
systems. The signal processing flow is created using a graphical
development tool supplied by Analog Devices, which allows fast
development of even complex audio flows and real-time control
of all signal processing functions.
The input and output word lengths are 24 bits. Four extra head-
room bits are used in the processor to allow internal gains of up
to 24 dB without clipping.
The signal processing blocks can be arranged in a custom program
that is loaded to the RAM of the ADAV400. The available signal
processing blocks are outlined in the
Programming sections.
NUMERIC FORMATS
It is common in DSP systems to use a standardized method of
specifying numeric formats. Fractional number systems are
specified by an A.B format, where A is the number of bits to the
left of the decimal point and B is the number of bits to the right
of the decimal point.
The ADAV400 uses the same numeric format for both the
coefficient values (stored in the parameter RAM) and the signal
data values.
Numeric Format: 5.23
Range
−16.0 to (+16.0 − 1 LSB)
Examples
1000 0000 0000 0000 0000 0000 0000 = −16.0
1110 0000 0000 0000 0000 0000 0000 = −4.0
1111 1000 0000 0000 0000 0000 0000 = −1.0
1111 1110 0000 0000 0000 0000 0000 = −0.25
1111 1111 1111 1111 1111 1111 1111 = (1 LSB below 0.0)
0000 0000 0000 0000 0000 0000 0000 = 0.0
0000 0010 0000 0000 0000 0000 0000 = +0.25
0000 1000 0000 0000 0000 0000 0000 = +1.0
0010 0000 0000 0000 0000 0000 0000 = +4.0
0111 1111 1111 1111 1111 1111 1111 = (+16.0 − 1 LSB)
The serial port accepts up to 24 bits on the input and is sign-
extended to the full 28 bits of the core. This allows internal
gains of up to 24 dB without encountering internal clipping.
Numeric Formats and
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A digital clipper circuit is used between the output of the DSP
core and the serial output ports (see Figure 22). This clips the
top four bits of the signal to produce a 24-bit output with a
range of +1.0 (−1 LSB) to −1.0.
DATA IN
PROGRAMMING
On power-up, the default program of the ADAV400 passes the
unprocessed input signals to the outputs, but the outputs are
muted by default. There are 2560 instruction cycles per audio
sample. This DSP runs in a stream-oriented manner, meaning
all 2560 instructions are executed each sample period. The
ADAV400 can also be set up to accept double- or quad-speed
inputs by reducing the number of instructions per sample. This
is set in the audio core control register.
The part is easily programmed using graphical tools provided
by Analog Devices. No knowledge of DSP assembly code is
required to program the ADAV400. Simply connect graphical
blocks, such as biquad filters, dynamics processors, mixers, and
delays, in a signal flow schematic. The schematic is then
compiled, and the program and parameter files are loaded into
the program RAM of the ADAV400 through the control port.
Signal processing blocks available in the provided libraries include
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Additional blocks are always in development. Analog Devices
also provides proprietary and third-party algorithms for appli-
cations such as matrix decoding, bass enhancement, and surround
virtualizers. Contact Analog Devices for information about
licensing these algorithms.
Single- and double-precision biquad filters
Monochannel and multichannel dynamics processors
Mixers and splitters
Tone and noise generators
First-order filters
Fixed and variable gain
RMS look-up tables
Loudness
Delay
Stereo enhancement (Phat Stereo™)
Dynamic bass boost
Interpolators and decimators
Figure 22. Numeric Precision and Clipping Structure
SERIAL PORT
4-BIT SIGN EXTENSION
1.23
5.23
SIGNAL PROCESSING
(5.23 FORMAT)
5.23
CLIPPER
DIGITAL
1.23