University:
California State University, Northridge
Course:
COMP 108 | Orientation to Computer Science
Academic year:

2024
Views:

267

Pages:

19
Author:

Matilda Mckee

Introduction Why go digital?   Digital signal processing techniques are now so powerful that sometimes it is extremely difficult, if not impossible, for analogue signal processing to achieve similar performance. Examples:   FIR filter with linear phase. Adaptive filters. Why go digital?  Analogue signal processing is achieved by using analogue components such as:     Resistors. Capacitors. Inductors. The inherent tolerances associated with these components, temperature, voltage changes and mechanical vibrations can dramatically affect the effectiveness of the analogue circuitry. Why go digital?  With DSP it is easy to:     Change applications. Correct applications. Update applications. Additionally DSP reduces:      Noise susceptibility. Chip count. Development time. Cost. Power consumption. Why NOT go digital?  High frequency signals cannot be processed digitally because of two reasons:   Analog to Digital Converters, ADC cannot work fast enough. The application can be too complex to be performed in real-time. Real-time processing    DSP processors have to perform tasks in real-time, so how do we define realtime? The definition of real-time depends on the application. Example: a 100-tap FIR filter is performed in real-time if the DSP can perform and complete the following operation between two samples: 99 y (n ) = ∑ a(k )x(n − k ) k =0 Real-time processing Processing Time n  Waiting Time Sample Time n+1 We can say that we have a real-time application if:  Waiting Time ≥ 0 Why do we need DSP processors?  Why not use a General Purpose Processor (GPP) such as a Pentium instead of a DSP processor?   What is the power consumption of a Pentium and a DSP processor? What is the cost of a Pentium and a DSP processor? Why do we need DSP processors?  Use a DSP processor when the following are required:      Cost saving. Smaller size. Low power consumption. Processing of many “high” frequency signals in real-time. Use a GPP processor when the following are required:   Large memory. Advanced operating systems. What are the typical DSP algorithms?  The Sum of Products (SOP) is the key element in most DSP algorithms: Algorithm Finite Impulse Response Filter Equation y ( n) = M ∑a k x(n − k ) k =0 Infinite Impulse Response Filter y ( n) = M ∑a k k =0 Convolution y ( n) = x ( n − k )+ N ∑b k y (n − k ) k =1 N ∑ x ( k ) h( n − k ) k =0 Discrete Fourier Transform X (k ) = N −1 ∑ x(n) exp[− j(2π / N )nk ] n =0 Discrete Cosine Transform F (u ) = N −1  π  ∑ c(u). f ( x). cos 2 N u(2 x + 1) x =0 Hardware vs. Microcode multiplication    DSP processors are optimised to perform multiplication and addition operations. Multiplication and addition are done in hardware and in one cycle. Example: 4-bit multiply (unsigned). Hardware Microcode 10011010 0000 1011. 1011.. 1011... 1011 x 1110 1011 x 1110 10011010 Cycle Cycle Cycle Cycle 1 2 3 4 Cycle 5 Parameters to consider when choosing a DSP processor Parameter TMS320C6211 (@150MHz) 32-bit TMS320C6711 (@150MHz) 32-bit N/A 64-bit Extended Arithmetic 40-bit 40-bit Performance (peak) 1200MIPS 1200MFLOPS 2 (16 x 16-bit) with 32-bit result 2 (32 x 32-bit) with 32 or 64-bit result 32 32 Internal L1 program memory cache 32K 32K Internal L1 data memory cache 32K 32K Internal L2 cache 512K 512K Arithmetic format Extended floating point Number of hardware multipliers Number of registers Parameters to consider when choosing a DSP processor Parameter TMS320C6211 (@150MHz) 2 x 75Mbps TMS320C6711 (@150MHz) 2 x 75Mbps 16 16 Not inherent Not inherent 3.3V I/O, 1.8V Core 3.3V I/O, 1.8V Core Yes Yes On-chip timers (number/width) 2 x 32-bit 2 x 32-bit Cost US$ 21.54 US$ 21.54 256 Pin BGA 256 Pin BGA External memory interface controller Yes Yes JTAG Yes Yes I/O bandwidth: Serial Ports (number/speed) DMA channels Multiprocessor support Supply voltage Power management Package Floating vs. Fixed point processors  Applications which require:      High precision. Wide dynamic range. High signal-to-noise ratio. Ease of use. Need a floating point processor. Drawback of floating point processors:    Higher power consumption. Can be more expensive. Can be slower than fixed-point counterparts and larger in size. Floating vs. Fixed point processors   It is the application that dictates which device and platform to use in order to achieve optimum performance at a low cost. For educational purposes, use the floating-point device (C6713) as it can support both fixed and floating point operations. General Purpose DSP vs. DSP in ASIC   Application Specific Integrated Circuits (ASICs) are semiconductors designed for dedicated functions. The advantages and disadvantages of using ASICs are listed below: Advantages Disadvantages • • • • • • • • • High throughput Lower silicon area Lower power consumption Improved reliability Reduction in system noise Low overall system cost High investment cost Less flexibility Long time from design to market Texas Instruments’ TMS320 family  Different families and sub-families exist to support different markets. C2000 C5000 C6000 Lowest Cost Efficiency Performance & Best Ease-of-Use Control Systems  Motor Control  Storage  Digital Ctrl Systems Best MIPS per Watt / Dollar / Size  Wireless phones  Internet audio players  Digital still cameras  Modems  Telephony  VoIP        Multi Channel and Multi Function App's Comm Infrastructure Wireless Base-stations DSL Imaging Multi-media Servers Video TMS320C64x: The C64x fixed-point DSPs offer the industry's highest level of performance to address the demands of the digital age. At clock rates of up to 1 GHz, C64x DSPs can process information at rates up to 8000 MIPS with costs as low as $19.95. In addition to a high clock rate, C64x DSPs can do more work each cycle with built-in extensions. These extensions include new instructions to accelerate performance in key application areas such as digital communications infrastructure and video and image processing. TMS320C62x: These first-generation fixed-point DSPs represent breakthrough technology that enables new equipments and energizes existing implementations for multi-channel, multi-function applications, such as wireless base stations, remote access servers (RAS), digital subscriber loop (xDSL) systems, personalized home security systems, advanced imaging/biometrics, industrial scanners, precision instrumentation and multichannel telephony systems. TMS320C67x: For designers of high-precision applications, C67x floatingpoint DSPs offer the speed, precision, power savings and dynamic range to meet a wide variety of design needs. These dynamic DSPs are the ideal solution for demanding applications like audio, medical imaging, instrumentation and automotive. C6000 Roadmap Object Code Software Compatibility Floating Point Performance Multi-core 2nd Generation C6412 C6414 C6411 C64x DSP 1.1 GHz C6416 C6415 DM642 1st Generation C6201 C6202 C6701 C6203 C6211 C6713 C6204 C6205 C6711 C6712 C62x/C64x/DM642: Fixed Point C67x: Floating Point Time

Digital Signal Processing

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