Uploaded byAbhishek Tiwari
Dsp Datapath
The document discusses the design of a data path architecture for digital signal processors (DSPs), detailing components such as registers, multipliers, and arithmetic logic units (ALUs). It covers the functionality of important modules like the multiply-accumulate (MAC) unit, control unit, and shifter, while emphasizing the design's focus on performance, efficiency, and application in various technologies. The presentation includes specific control signals, data-width considerations, and findings related to low-power applications and integration challenges.
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Dsp Datapath
- 1. AMini Project SeminaronDSPDATAPATHM.Tech MicroelectronicsManipal Institute of TechnologyBy:Abhishek TiwariB. Dhaval KumarK .Sravan KumarRajkumar Patidar
- 2. Introduction DatapathArchitecture of DatapathDatapath in DSP ProcessorsModules using in DatapathModules Function
- 3. Problem Definition DSPsPerformsall key arithmetic operations in 1 cycle.
- 4. Hardware support formanaging numeric fidelity:
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- 8. Shifts often take>1 cycle
- 9. Other operations typically take multiple cyclesDataPath:A datapath is a collection of functional units, registers, buffers.Most central processing units consist of a datapath and a control unit.Processor has Two Main Units in its Architecture
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- 11. DatapathSecond Main Partin Microprocessor.Contains Several Unit.It Referred RTL Design.
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- 13. A Simple DSPProcessor
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- 16. RegistersStoring Multiple BitsRegisterFile Synchronized by same Clock8 Bit Register, 16 Bit Register
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- 19. 4 x 8Register File
- 20. Design SummaryWord Length:8 bit, 16 bit
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- 22. Modeling : Behavioral Modeling
- 23. Used Generic Statement,If – Else Statement
- 24. ACC Reg.is 16 bit.
- 25. A load controlSignal for enabling Storing function.
- 26. A Clear forreset the stored value.
- 27. Functions on FallingEdge. Register’s Result
- 28. Multiply-Accumulate (MAC)What isMAC ?Multiplication followed by accumulation.Where is MAC Use ?Common operation in many digital systems, particularly those highly interconnected, like digital filters, neural networks, data quantizers, etc.What are the Features of MAC ?Multiplying two values ,then adding the result to the previously accumulated value, which must then be re-stored in the registers for future accumulations and Checking for Overflow.
- 29. Basic MAC UnitTypes of Multiplier:1.Unsigned Multiplier2. Signed Multiplier
- 30. Design Summary MACis 8-bit A,B: 8 bit I/P Registers prod: 16 bit O/P Register2 Control Signals :- Start and StopOverflow Function, which might happen when the number of MAC operations is large.Signed Adder
- 31. Timing Diagram &Result
- 32. Arithmetic Logic UnitIt consists of arithmetic and logic unit.Arithmetic Operation : Addition SubtractionLogical Operation : And,or,not etc..It performs the operations according to control signal givenIt is basic building block of microprocessor.
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- 35. Design Summary ALUis 16-bit A,B: 16 bit i/p reg y: 16 bit o/p registerControl Signal is of 4-bitIt can support up to 16 different operations.There is a separate flag register for carry and borrow, parity and sign flag.Comparator is also included in this Alu design.ALU is working on falling edge clock.
- 36. Design Details:Addition variable q: std_logic_vector(16 downto 0); when "0000" => q := ('0'& a) + ('0'& b); y <= q(15 downto 0); if ( q(16) = '1' ) then f(3) <= '1'; --carry flag end if; f(1) <= '0'; --Sign flag is zero Cont………
- 37. Cont….Subtraction variable q :std_logic_vector(16 downto 0); when "0001" => q := ('0'& a) - ('0'& b); y <= q(15 downto 0); if ( q(16) = '1' ) then f(1) <= '1'; --sign flag end if; f(3) <= '0'; --Carry flag is zero
- 38. Cont…Parity and Zeroflag variable p,z : std_logic; We are checking results separately for parity and zero flag for all the operations.Parity flag (even): p := y(15) xor y(14)……..…xor y(0); if ( p = '0') then f(2) <= '1';Zero flag: z := y(15) or y(14)……..…or y(0); if (z = '0') then f(0) <= '1';
- 39. Cont…Comparator when "1110" => if(a>b)then y<="0000000000000100"; elsif(a<b)then y<="0000000000000010";elsif(a=b)then y<="0000000000000001"; f(3) <= '0'; f(1) <= '0'; Here instead of extra resistor for comparator o/p, o/p resistery is used for comp o/pt to save one resister.At later stage we can use this results by using first 3 bit of o/p resister.
- 40. Cont…Other function when “case"=> y <= a “function” b; f(3) <= '0'; f(1) <= '0';Syntax for functions other then addition, subtraction and comparator is like above.For these functions sign flag and zero flag is always zero.
- 41. Control Word forDifferent Functions1000 XNOR
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- 47. 1110 CompareA & B
- 48. 1111 Reseto/p0000 Addition0001 Subtraction0010 AND0011 OR0100 NAND0101 NOR0110 NOT A0111 XOR
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- 50. ShifterThe shifter isused for shifting bits one position either to the left or to the right.The Shifter operations are referred to either as shifting or rotating depends on how the end bits are shifted in or out.Here Shown Simple Shifter :
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- 52. Design SummaryWord Length:16 bit Modeling : Behavioral ModelingUsed case statements and if else statements.A ‘shift_sel’ 2-bit control Signal for selecting type of shift.Functions on Falling Edge.Operations: 00 – No Operation 01 – Left shift by 8 bit 10 – Right shift by 8 bit 11 – Rotate Right by 8 bit
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- 54. Tristate BufferA TristateBuffer, as the name suggest, has three states: 0, 1 & Z.Z : Represents High Impedance State
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- 56. What is ControlUnitThe Control Unit inside the Processor is a FSM.By Stepping through a Sequence of States, it controls the operation of Datapath.Contains Next – State circuit, State Memory Register & Output Logic circuit.Control Inputs, Status Signals.Control output, Control Signal or Control Word.
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- 59. Control SignalsFor Registers:Load and Clear Signals1 bit Start signal for enable & disable the operation of MAC unitShifter operation depend on shift_sel signal.ALU has 4 bit control signal for performing operation alu_sel.Tristate Buffer has Out_en control signal.
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- 62. ConclusionDesigned to supporthigh-performance, repetitive, numerically intensive tasks.Ability to complete several accesses to memory in a single instruction cycle.Performance, cost, integration, ease of development, power consumption, and other factors for the application at hand.Datapath functions have become the dominant logic type in complex logic devices.
- 63. ApplicationsFrom radar systemsto consumer electronics.DSP data path synthesis for low-power applications.Application-specific function units.
- 64. Web Links &InformationDigital Logic and Microprocessor Design by Enoch O. Hwang
- 65. Circuit design withVHDL by Volnei A. Pedroni
- 66. A VHDL Primerby J. BhaskerThank You