adau1442 Analog Devices, Inc., adau1442 Datasheet - Page 59

• Manufacturer Part Number: adau1442
• Description: Sigmadsp Digital Audio Processor With Flexible Audio Routing Matrix
• Manufacturer: Analog Devices, Inc.

DSP CORE
The DSP core performs calculations on audio data as specified
by the instruction codes stored in program RAM. Because
SigmaStudio generates the instructions, it is not necessary to
have a detailed knowledge of the DSP core to use the SigmaDSP,
but a brief description is provided in this section.
Architecture
The core consists of a simple 28-/56-bit multiply-accumulate
unit (MAC) with two sources: a data source and a coefficient
source. The data source can come from the data RAM, a ROM
table of commonly used constant values, or the audio inputs to
the core. The coefficient source can come from the parameter
RAM, a ROM table of commonly used constant values, or the
audio inputs to the core. The two sources are multiplied in a
28-bit fixed-point multiplier and then the signal is input to the
56-bit adder; the result is usually stored in one of three 56-bit
accumulator registers. The accumulators can be output from the
core (in 28-bit format) or can optionally be written back into
the data or parameter RAMs.
ROM CONSTANTS,
DATA SOURCE
(DATA RAM,
INPUTS, ...)
(ACCUMULATORS (3), dB CONVERSION,
28
BIT OPERATORS, BIT SHIFTER, ...)
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Figure 51. Simplified Core Architecture
DATA OPERATIONS
TRUNCATOR
OUTPUTS
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56
28
56
COEFFICIENT SOURCE
(PARAMETER RAM,
ROM CONSTANTS,
INPUTS, ...)
Features
The SigmaDSP core was designed specifically for audio processing
and therefore includes several features intended for maximizing
efficiency. These include hardware decibel conversion and audio-
specific ROM constants.
Signal Processing
The ADAU144x is designed to provide all signal processing
functions commonly used in stereo or multichannel playback
systems. The signal processing flow is designed using
SigmaStudio software from Analog Devices. This software
allows graphical entry and real-time control of all signal
processing functions.
Many of the signal processing functions are coded using full,
56-bit, double-precision arithmetic. The serial port input and
output word lengths are 24 bits, but four extra headroom bits
are used in the processor to allow internal gains of up to 24 dB
without clipping. Additional gains can be achieved by initially
scaling down the input signal in the DSP signal flow.
28
TRUNCATOR
28
56