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DIGITAL SIGNAL PROCESSING

DIGITAL SIGNAL PROCESSING

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DIGITAL SIGNAL PROCESSING

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  1. DIGITAL SIGNAL PROCESSING Dr. Hugh Blanton ENTC 4337/ENTC 5337

  2. Outline • Signal processing applications • Conventional DSP architecture • TI TMS320C6000 DSP architecture introduction • Signal processing on general-purpose processors • Conclusion Dr. Blanton - ENTC 4337 - General Architecture 2

  3. Signal Processing Applications • Embedded system demand: product volume matters • 400 Million units/year: automobiles, PCs, and cell phones • 30 Million units/year: ADSL modems and printers • Embedded system cost and input/output rates • Low-cost, medium-throughput: low-end printers,wireless handsets, sound cards, car audio, disk drives • High-cost, high-throughput: high-end printers,wireless basestations, 3-D sonar, 3-D images from2-D X-rays (tomographic reconstruction) • Embedded processor requirements • Inexpensive with small area and volume • Predictable input/output (I/O) rates to/from processor • Power constraints (severe for handheld devices) Single DSP Multiple DSPs Dr. Blanton - ENTC 4337 - General Architecture 3

  4. Conventional DSP Processors • Low cost: $3/processor in volume • Deterministic interrupt service routine latency guarantees predictable input/output rates • On-chip direct memory access (DMA) controllers • Processes streaming input/output separately from CPU • Sends interrupt to CPU when block has been read/written • Ping-pong buffering • CPU reads/writes buffer 1 while DMA reads/writes buffer 2 • When DMA finishes with buffer 2, roles of buffer 1 & 2 switch Dr. Blanton - ENTC 4337 - General Architecture 4

  5. Conventional DSP Processors • Low power consumption: 10-100 mW • TI TMS320C54 0.32 mA/MIP  76.8 mW at 1.5 V, 160 MHz • TI TMS320C55 0.05 mA/MIP  22.5 mW at 1.5 V, 300 MHz Dr. Blanton - ENTC 4337 - General Architecture 5

  6. Conventional DSP Architecture • Multiply-accumulate (MAC) in one instruction cycle • Harvard architecture for fast on-chip input/output • Data memory/bus(es) separate from program memory/bus • One read from program memory per instruction cycle • Two reads/writes from/to data memory per instruction cycle • Instructions to keep pipeline (3-6 stages) full • Zero-overhead looping (one pipeline flush to set up) • Delayed branches • Special addressing modes supported in hardware • Bit-reversed addressing (e.g. fast Fourier transforms) • Modulo addressing for circular buffers (e.g. FIR filters) Dr. Blanton - ENTC 4337 - General Architecture 6

  7. Data Shifting Time Buffer contents Next sample xN-K+1 xN-1 xN+1 xN-K+2 xN n=N xN-K+2 xN xN-K+3 xN+1 n=N+1 xN+2 xN-K+3 xN+1 xN-K+4 xN+2 n=N+2 xN+3 Conventional DSP Architecture (con’t) • Buffer of length K • Used in finite and infinite impulse response filters • Linear buffer • Order by time index • Data shifting update: discard oldest data, copy old data left, insert new data Dr. Blanton - ENTC 4337 - General Architecture 7

  8. Modulo Addressing Time Next sample Buffer contents n=N xN-2 xN-K+1 xN xN+1 xN-1 xN-K+2 xN+2 xN-2 xN+1 xN xN xN-K+3 xN-1 xN-K+2 n=N+1 xN-2 xN+1 xN xN-1 xN xN+2 xN-K+3 xN-K+4 xN-K+4 n=N+2 xN+3 Conventional DSP Architecture (con’t) • Circular buffer • Index oldest sample • Modulo addressing update: insert new data at oldest index, update oldest index Dr. Blanton - ENTC 4337 - General Architecture 8

  9. Conventional DSP Processors Summary Dr. Blanton - ENTC 4337 - General Architecture 9

  10. Conventional DSP Processor Families DSP Market Fixed-point 95%Floating-point 5% • Floating-point DSPs • Used in first pass prototyping of algorithms • Resurgence due to professional and car audio • Different on-chip configurations in each family • Size and map of data and program memory • A/D, input/output buffers, interfaces, timers, and D/A • Drawbacks to conventional DSP processors • No byte addressing (needed for images and video) • Limited on-chip memory • Limited addressable memory on fixed-point DSPs (exceptions include Motorola 56300 and TI C5409) • Non-standard C extensions for fixed-point data type Dr. Blanton - ENTC 4337 - General Architecture 10

  11. TI TMS320C6000 DSP Architecture Simplified Architecture Program RAM Data RAM or Cache Addr Internal Buses DMA Serial Port Host Port Boot Load Timers Pwr Down Data .D1 .D2 .M1 .M2 External Memory -Sync -Async Regs (A0-A15) Regs (B0-B15) .L1 .L2 .S1 .S2 Control Regs CPU Dr. Blanton - ENTC 4337 - General Architecture 11

  12. TI TMS320C6000 DSP Architecture • Families: All support same C6000 instruction set • C6200 fixed-point 150- 300 MHz ADSL, printers • C6400 fixed-point 300-1,000 MHz video/comm. apps. • C6700 floating-point 100- 225 MHz medical imaging, pro-audio • TMS320C6211: 150 MHz, $21 in volume • 300 million multiply-accumulates/s, 1200 RISC MIPS • On-chip memory: 16 kwords program, 16 kwords data • TMS320C6701 Evaluation Module Board 167 MHz • 334 million multiply-accumulates/s, 1336 RISC MIPS • On-chip memory: 16 kwords program, 16 kwords data • External: one 133-MHz 64-kword, two 100-MHz 1-Mword Dr. Blanton - ENTC 4337 - General Architecture 12

  13. TI TMS320C6000 DSP Architecture • Very long instruction word (VLIW) size of 256 bits • Eight 32-bit functional units with single cycle throughput • One instruction cycle per clock cycle • Data word size is 32 bits • 16 (32 on C64) 32-bit registers in each of two data paths • 40 bits can be stored in adjacent even/odd registers • Two parallel data paths • Data unit - 32-bit address calculations (modulo, linear) • Multiplier unit - 16 bit  16 bit with 32-bit result • Logical unit - 40-bit (saturation) arithmetic & compares • Shifter unit - 32-bit integer ALU and 40-bit shifter Dr. Blanton - ENTC 4337 - General Architecture 13

  14. TI TMS320C6000 Instruction Set C6000 Instruction Set by Functional Unit .S Unit ADD NEGADDK NOTADD2 ORAND SETB SHLCLR SHREXT SSHLMV SUBMVC SUB2MVK XORMVKH ZERO .L Unit ABS NOTADD ORAND SADDCMPEQ SATCMPGT SSUBCMPLT SUBLMBD SUBCMV XORNEG ZERONORM .D Unit ADD STADDA SUBLD SUBAMV ZERONEG .M Unit MPY SMPYMPYH SMPYH Other NOP IDLE Six of the eight functional units can perform integer add, subtract, and move operations Dr. Blanton - ENTC 4337 - General Architecture 14

  15. TI TMS320C6000 Instruction Set ArithmeticABSADDADDAADDKADD2MPYMPYHNEGSMPYSMPYHSADDSATSSUBSUBSUBASUBCSUB2ZERO LogicalANDCMPEQCMPGTCMPLTNOTORSHLSHRSSHLXOR DataManagementLDMVMVCMVKMVKHST ProgramControlBIDLENOP BitManagementCLREXTLMBDNORMSET C6000 InstructionSet by Category (un)signed multiplicationsaturation/packed arithmetic Dr. Blanton - ENTC 4337 - General Architecture 15

  16. C6000 vs. C5000 Addressing Modes • Immediate • The operand is part of the instruction • Register • Operand is specified in a register • Direct • Address of operand is part of the instruction (added to imply memory page) • Indirect • Address of operand is stored in a register TI C5000 TI C6000 ADD #0FFh add .L1 -13,A1,A6 (implied) add .L1 A7,A6,A7 ADD 010h not supported ADD * ldw .L1 *A5++[8],A1 Dr. Blanton - ENTC 4337 - General Architecture 16

  17. TI TMS320C6000 DSP Architecture • Deep pipeline • 7-11 stages in C6200: fetch 4, decode 2, execute 1-5 • 7-16 stages in C6700: fetch 4, decode 2, execute 1-10 • Pentium IV has an estimated 20 pipeline stages • Avoid using branch instructions in code • Branch instruction in pipeline disables interrupts: latency of a branch is 5 cycles • Avoid branches by using conditional execution: every instruction can be conditionally executed • No hardware protection against pipeline hazards • Compiler and assembler must prevent pipeline hazards Dr. Blanton - ENTC 4337 - General Architecture 17

  18. TI TMS320C6700 Extensions C6700 Floating Point Extensions by Unit .S Unit ABSDP CMPLTSP ABSSP RCPDPCMPEQDP RCPSP CMPEQSP RSARDP CMPGTDP RSQRSP CMPGTSP SPDPCMPLTDP .L Unit ADDDP INTSPADDSP SPINTDPINT SPTRUNCDPSP SUBDPDPTRUNC SUBSPINTDP .M Unit MPYDP MPYIDMPYI MPYSP .D Unit ADDAD LDDW Four functional units can perform IEEE single-precision (SP) and double-precision (DP) floating-point add, subtract, move. Operations beginning with R are reciprocal calculations. Dr. Blanton - ENTC 4337 - General Architecture 18

  19. Digital Signal Processor Cores • ASIC with • Programmable digital signal processor core • RAM • ROM • Standard cells • Codec • Peripherals • Gate array • Microcontroller core Application Specific Integrated Circuit Dr. Blanton - ENTC 4337 - General Architecture 19

  20. General Purpose Processors • Multimedia applications on PCs • Video, audio, graphics and animation • Repetitive parallel sequences of instructions • Single Instruction Multiple Data (SIMD) • One instruction acts on multiple data in parallel • Well-suited for graphics • Native signal processing extensions use SIMD • Sun Visual Instruction Set [1995] (UltraSPARC 1/2) • Intel MMX [1996] (Pentium I/II/III/IV) • Intel Streaming SIMD Extensions (Pentium III) Dr. Blanton - ENTC 4337 - General Architecture 20

  21. DSP on General Purpose Processors (con’t) • Programming is considerably tougher • Ability of compilers to generate code for instruction set extensions may lag (e.g. four years for Pentium MMX) • Libraries of routines using native signal processing • Hand code in assembly for best performance • Single-instruction multiple-data (SIMD) approach • Pack/unpack data not aligned on SIMD word boundaries • Saturation arithmetic in MMX; not supported in VIS • Extended-precision accumulation in MMX; none in VIS • Application speedup for Intel MMX and Sun VIS • Signal and image processing: 1.5:1 to 2:1 • Graphics: 4:1 to 6:1 (no packing/unpacking) Dr. Blanton - ENTC 4337 - General Architecture 21

  22. Concluding Remarks • Conventional digital signal processors • High performance vs. power consumption/cost/volume • Excellent at one-dimensional processing • Per cycle: 1 16  16 MAC & 4 16-bit RISC instructions • TMS320C6000 VLIW DSP family • High performance vs. cost/volume • Excellent at multidimensional signal processing • Per cycle: 2 16  16 MACs & 4 32-bit RISC instructions • Native signal processing • Available on desktop computers • Excels at graphics • Per cycle: 2 8  16 MACs OR 8 8-bit RISC instructions • Use assembly for computational kernels and C for main program (control code, interrupt def.) Dr. Blanton - ENTC 4337 - General Architecture 22

  23. Concluding Remarks • Digital signal processor market • 40% annual growth rate 1990-2000 fastest in semiconductor market • Revenue: $3.5B ‘98, $4.4B ‘99, $6.1B ‘00, $4.5B ‘01, $4.9B ‘02 • 2000: 44% TI, 23% Agere, 13% Motorola, 10% Analog Devices • 2001: 40% TI, 16% Agere, 12% Motorola, 8% Analog Devices • 2002: 43% TI, 14% Motorola, 14% Agere, 9% Analog Devices • Independent processor benchmarking by industry • Berkeley Design Technology Inc. http://www.bdti.com • EDN Embedded Microprocessor Benchmark Consortium http://www.eembc.org • Web resources • Newsgroup comp.dsp: FAQ http://www.bdti.com/faq/dsp_faq.html • Embedded processors and systems: http://www.eg3.com • On-line courses: http://www.techonline.com Dr. Blanton - ENTC 4337 - General Architecture 23

  24. Concluding Remarks • Web resources • Newsgroup comp.dsp: FAQ http://www.bdti.com/faq/dsp_faq.html • Embedded processors and systems: http://www.eg3.com • On-line courses: http://www.techonline.com Dr. Blanton - ENTC 4337 - General Architecture 24