
1.
General description
The SAF784x is a single-chip solution CD audio decoder with on-chip MP3 and WMA
decoding, digital servo, audio DAC, sample-rate converter, preamplifier, laser driver and
integrated ARM7TDMI-S microprocessor. The device contains all of the required ROM
and RAM, including an internal re-programmable Flash ROM, and is targeted at low-cost
compressed audio CD applications. The design is a one-chip CD audio decoder IC, with
additions to allow low-cost system implementation of MP3 and WMA decoding.
2.
Features
2.1 Features
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Channel decoder and digital servo
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32-bit embedded ARM7 RISC microprocessor supporting both 32-bit and 16-bit
(‘Thumb’) instruction sets
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Maximum ARM operating frequency of 76 MHz, equivalent to 68 MIPS
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Decoding of compressed audio stream (MP3/WMA) on ARM7 core
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All memories required for MP3/WMA decoding embedded on chip: combination of
130 kB mask-programmed internal program ROM (to reduce wait-states on
high-speed code, e.g. decompression algorithms), 42 kB boot ROM, 64 kB of internal
re-programmable Flash ROM (for simple re-programming of application code) 110 kB
internal SRAM
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Programmable clock frequency for ARM microprocessor - allowing users to trade-off
power consumption and processing power depending on requirements
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Block decoder hardware to perform C3 error correction
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Sample-rate converter circuit to convert compressed audio sample rates (in the range
8 kHz to 48 kHz) to an output rate of 44.1 kHz
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Microprocessor access to digital representations of the diode input signals from the
optical pickup; the microprocessor can also generate the servo output signals RA, FO,
SL, allowing the possibility of additional servo algorithms in software
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Programmable PDM outputs (effectively sine and cosine) to allow use of stepper motor
for sledge mechanism
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Microprocessor access to audio streams, both from the internal CD decoder and an
external stereo auxiliary input (e.g. an analog source from a tuner, converted to digital
via on-chip ADCs) to allow audio processing algorithms in the ARM microprocessor,
e.g. bass boost, volume control
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Four general-purpose analog inputs (A_IN1 to A_IN4) allowing the ARM
microprocessor access to other external analog signals, e.g. low-cost keypad,
temperature sensor, via on-chip ADCs
SAF784x
One chip CD audio device with integrated MP3/WMA decoder
Rev. 02 — 9 May 2008
Product data sheet