An Introduction to Digital System Design

M.Mohajjel

Digital System Design 2

Digital Systems Advantages

Ease of designReproducibility of resultsNoise immunity Ease of Integration

DisadvantagesThe real world is analogA/D & D/A overhead

Digital System Design 3

Evolution of Digital SystemsThe earliest digital circuits

vacuum tubes & transistorsIntegrated circuits

SSI (Small Scale Integration) 10s of logic gates

MSI (Medium Scale Integration) 100s of logic gates

LSI (Large Scale Integration) 1000s of logic gates

VLSI (Very Large Scale Integration) 100,000s of logic gates

Need for Computer-Aided Design

Digital System Design 4

Digital System Design ProcessInitial design ideaBehavioral description (overall functionality)

Flow chartPseudo code

RTL description Data pathControl procedure

Digital System Design 5

Digital System Design Process (cont.)

Logic designNet list of gates & flip flops

Circuit & Physical designNet list of transistors

ManufacturingMasks for IC FabricationBit stream

Digital System Design 6

Digital System Design Process (cont.)SynthesisVerificationComputer aided design (CAD)

toolsSynthesis

From RTL description down to manufacturing

Verification Simulation Timing analysis Test generation

Digital System Design 7

Programmable Logic DevicesWhy?

TTM (Time-to-market)PrototypingReconfigurable and Custom Computing

Digital System Design 8

Hardware Description Languages (HDL)

Why?

Very large scale designs

Weakness of conventional programming

language in hardware modeling and

description

Compact description of hardware in

different design stages

Digital System Design 9

Hardware Description Languages (HDL) (cont.)

Hardware Description RequirementsConcurrencyTiming and DelaySupport for Design HierarchyReadability (Documentation)

Digital System Design 10

Hardware Description Languages (HDL) (cont.)

ExamplesPopular HDLs (IEEE standard)

Verilog = Verifying Logic VHDL = Very High Speed Integrated Circuit

Hardware Description Language

Other HDLs AHPL TI-HDL AHDL