DIGITAL SIGNAL PROCESSORS

What are Digital Signals?Digital signals have finite precision in both the time (sampled) and amplitude (quantized) domains.

What are Digital Signal Processors?

Digital Signal Processors are microprocessors optimized to perform digital signal processing tasks.

Uses of DSPsTelephone: Signal MultiplexingMilitary: RADARMedicine: MRIScientific: Spectral AnalysisIndustrial: Oil ProspectingCommercial: Movie Special Effects

Uses (contd…)

Characteristics of DSPs

Real-time processing

Limited data types (e.g. floating point)

Very Large Instruction Word (VLIW) architecture

Characteristics (contd…)DSPs are optimized for mathematical calculations (as opposed to data manipulation).

Characteristics (contd…)Harvard Architecture

Characteristics (contd…)Specialized registers (e.g. extended precision accumulators)

Onboard fast RAM, ROM, DMA

Massive Parallelism

Floating Point vs. Fixed Point

Advantages of Floating Point:PrecisionGreater Dynamic RangeShorter Development TimeBetter Signal-to-noise Ratio

Disadvantages of Floating Point:Expensive

Assembly vs. CAdvantages of Assembly

FasterRequires less memory

Disadvantages of AssemblyExpensiveHard to maintainIntimate knowledge of hardware required

Sample DSP: SMJ320C6701

Military DSP used in munitions guidance, avionics, navigation, electronic countermeasures, anti-submarine warfare, etc.

SMJ320C6701 (contd…)

Up to 1 GFLOPS at 167 MHzLoad/Store architecture

Instructions operate on data in registers

VLIW architectureIEEE floating point

Double precision 4 cycle throughputSingle precision 1 cycle throughput

Variable length execution packets

SMJ320C6701 (contd…)

CPUSMJ320C6701 (contd…)

Internal Program MemoryInternal Data MemoryHost Port Interface

Allows other processors access to internal DSP memory.

SMJ320C6701 (contd…)

Multichannel Buffered Serial PortAllows fast inter-processor communication

Direct Memory AccessFewer CPU interrupts

External Memory InterfaceGlueless interface to SBRAM, SRDRAM and SRAM

SMJ320C6701 (contd…)

Some SignalsCLOCK

CLKIN: clock inputCLKMODE: x4 or x1 output clock f

DMADMAC3,2,1,0: DMA action complete

EMIF controlCE3,2,1,0: memory space enables, enabled by bits 24 and 25 of word address

Bus ArbitrationHOLD: HOLD requestHOLDA: HOLD acknowledge

DRAM controlSDRAS: SDRAM row address strobeSDCAS: SDRAM column strobeSDWE: SDRAM write enableSDCLK: SDRAM clock

Some Signals (contd…)