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INTR ODUCTION TOF E P IX D OINT AND F OATING P L OINT P OCE S S R S OR Presented by: Sarbjeet Singh NITTTR-Chandigarh
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DSP PROCESSORS DATA FO RM T A Fixed point represent each no by with the minimum of 16 bits. Floating point take 32 bits to store each value2 FIXED POINT AND FLOATING POINT PROCESSORS 10/31/12
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F DP IXE OINT FORMATThere are four common ways that these 2^16 = 65,536 possible bitpatterns can represent a number3 FIXED POINT AND FLOATING POINT PROCESSORS 10/31/12
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FIXED POINT DATA FORMAT UNSIGNED INTEGER o The stored no can take one of any integer value from 0 to 65536 SIGNED INTEGER o Use two’s compliment to make the range o Include negative numbers that is from -32768 to 32767 UNSIGNED FRACTION NOTATION o The 65536 levels are spread uniformly between 0 and 1 SIGNED FRACTION FORMAT ALLOWS o Negative no, equally spaced between -1 to 14 FIXED POINT AND FLOATING POINT PROCESSORS 10/31/12
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F OAT L ING POINT FORMAT use a minimum of 32 bits to store each value 2^32 =4,294,967,296 This results in many more bit patterns than for fixed point A key feature of floating point notation is that the represented numbers are not uniformly spaced. All floating point DSPs can also handle fixed point numbers e.g.- SHARC processor5 FIXED POINT AND FLOATING POINT PROCESSORS 10/31/12
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F DP IXE OINT PROCESSORS Fixed point processor are………. Cheaper and less power consuming Use shorter data word width that will provide adequate accuracy Most of fixed point DSP processor use 16 bit data words •Sufficient for many applications Most DSP includes one or more accumulator registers •Wider than other registers •Provide extra guard bits to avoid overflow6 FIXED POINT AND FLOATING POINT PROCESSORS 10/31/12
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F D VE IXE RSUS F OAT L ING POINT DSP Fixed point DSPs are generally cheaper While floating point devices have •Better precision, •higher dynamic Range •shorter development cycle.7 FIXED POINT AND FLOATING POINT PROCESSORS 10/31/12
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F DP IXE OINT VS F OAT L ING POINT Fixed Point/Floating Point F IXE P D OINT P ROCE SSOR are : cheaper smaller less power consuming Harder to program Watch for errors: truncation, overflow, rounding Limited dynamic range Used in 95% of consumer products F OAT L ING P OINT P ROCE SSORS have larger accuracy are much easier to program can access larger memory It is harder to create an efficient program in C on a fixed point processors than on floating point processors8 FIXED POINT AND FLOATING POINT PROCESSORS 10/31/12
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PERFORMANCE WHAT 32 BIT FLOATING POINT SYSTEM CAN DO THAT 16 BIT FIXED POINT CAN’T ??????????????????? Provide HIGH SIGNAL TO NOISE RATIO9 FIXED POINT AND FLOATING POINT PROCESSORS 10/31/12
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the signal-to-noise ratio for storing a floating point number is about 30 million to one while for a fixed point number it is only abo ut te n-tho usand to o ne floating point has roughly 3,000 times less quantization noise than fixed point10 FIXED POINT AND FLOATING POINT PROCESSORS 10/31/12
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Fixed versus floating point instructions These are the multiplication instructions used in the SHARC DSPs. W hile only a single command is needed for floating point, many options are needed for fixed point.11 FIXED POINT AND FLOATING POINT PROCESSORS 10/31/12
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FIXED POINT VS FLOATING POINT Floating Point Fixed Point Applications Applications •Portable Products •Modems •2G, 2.5G and 3G Cell Phones •Digital Subscriber Line (DSL) •Digital Audio Players •Wireless Base stations •Digital Still Cameras •Central Office Switches •Electronic Books •Private Branch Exchange (PBX) •Voice Recognition •Digital Imaging •GPS Receivers •3D Graphics •Headsets •Speech Recognition •Biometrics •Fingerprint Recognition •Voice over IP12 FIXED POINT AND FLOATING POINT PROCESSORS 10/31/12
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DIGIT SIGNAL P AL ROCESSORS COM ANIE P S ANAL DEOG VICE S L NT T CH UCE E NOL OGIE S •ADSP-21xx-16 bit, fixed point •DSP 16xxx-16 bit, fixed point •ADSP-21xxx-32 bit, floating •DSP 32xx-32 bit, floating point point and fixed point M OR A OT OL T XAS INST E RUME S NT •DSP 561xx,16 bit, fixed point •TMS 320cxx,16 bit fixed •DSP 560xx,24 bit, fixed point point •DSP 96002,32 bit, floating •TMS 320cxxx,32 bit, floating point point13 FIXED POINT AND FLOATING POINT PROCESSORS 10/31/12
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CONCLUSION floating point and fixed point usually use 32 bits and 16 bits, respectively, but no t always. Fixed point processor are : Cheaper , smaller , less power consuming , Harder to program Watch for errors: truncation, overflow, rounding Limited dynamic range Floating point processors have larger accuracy , are much easier to program , can access larger memory14 FIXED POINT AND FLOATING POINT PROCESSORS 10/31/12
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REFERENCE I feachor & Jervis - Digital Signal Processing The Scie ntist and Eng ine e rs Guide to Dig ital Sig nal Pro ce ssing http://www.sundance.com/index.htm http://www.bdti.com/15 FIXED POINT AND FLOATING POINT PROCESSORS 10/31/12