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ASIC 120: Digital Systems and Standard-Cell ASIC Design

Learn about digital systems, combinational & sequential logic, including NOT, AND, OR, XOR, NAND gates, flip-flops, state machines, and how to construct circuits.

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ASIC 120: Digital Systems and Standard-Cell ASIC Design

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  1. ASIC 120: Digital Systems and Standard-Cell ASIC Design Tutorial 1: Introduction to Digital Circuits October 11, 2005

  2. Outline • Digital Systems • Combinational Logic • NOT, AND, OR, XOR, NAND, etc. • mux, half-adder, full-adder • Sequential Logic • flip-flop/register, shift register, counter • state machines

  3. Digital Systems • Analog vs. Digital • continuously varying vs. discrete • imprecise vs. precise • 0..1 vs. 0 or 1 • Digital systems excel at… • repetitive calculations • large amounts of data • reproducible results

  4. The Big Picture

  5. The Big Picture

  6. Combinational and Sequential Logic • We can break a digital system into two types of logic • Combinational • computation happens in a linear fashion • Sequential • computation involves a feedback loop (memory)

  7. Combinational Logic: NOT Truth Table Input Output

  8. Combinational Logic: AND

  9. Combinational Logic: OR

  10. Combinational Logic: XOR

  11. Combinational Logic: NAND

  12. Combinational Logic: NOR, XNOR

  13. Building Combinational Circuits

  14. Combinational Logic: MUX(multiplexer)

  15. Half Adder

  16. Full Adder

  17. Full Adder

  18. What I’ve Skipped • Gates with more than two inputs • Boolean algebra • Karnaugh maps • Quine-McCluskey method • Binary arithmetic, base conversions • Practical digital circuits have more than 0s and 1s • Transmission gates, tri-state buffers

  19. Sequential Logic

  20. Basic Feedback Element: SR latch

  21. D Flip-Flop or Register

  22. Synchronous vs. Asynchronous • Synchronous • circuit operation governed by a clock • currently more popular and practical • Asynchronous • circuit operation independent of a clock • potentially faster than synchronous • lower power consumption • difficult to design

  23. Sequential Constructs • Shift register • Counter • State Machines

  24. State Machines • Useful abstract constructs for more complex sequential logic

  25. What I’ve Skipped • Other flip-flops (RS, T, JK) • Other interesting sequential circuits (barrel shifters, etc.)

  26. Hardware Description Languages (HDLs) • HDL describes in text a digital circuit • Examples • VHDL (we will look at this next time) • Verilog • AHDL • JHDL

  27. Hardware Description Languages (HDLs) • schematics are useful for… • drawing high level diagrams • manually working out simple pieces of logic • HDLs are useful for… • describing complex digital systems • HDLs are not... • software programming languages (C, Java, assembly, etc.)

  28. Summary • Digital Systems • Combinational Logic • NOT, AND, OR, XOR, NAND, etc. • mux, half-adder, full-adder • Sequential Logic • flip-flop/register, shift register, counter • state machines

  29. UW ASIC Design Team • www.asic.uwaterloo.ca • reference material • Bryce Leung’s tutorials (UW ASIC website) • Michael Goldsmith’s tutorials (UW ASIC website) • your course notes • my contact info: Jeff Wentworth, jswentwo@engmail.uwaterloo.ca

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