Learning Digital Design

Digital Design & Analog Design

  • All components that go in to an SOC can be divided in to either digital or analog
  • All these components involve various digital and analog design concepts starting CMOS, gates, delays, latch, flip flop, etc to name a few
  • As a fresher it is essential to know all these concepts for multiple reasons
  • o Learning above concepts, makes it easy to understand advanced concepts as you move to learn protocols like PCIe, USB, DDR, AXI, etc
  • o Majority of interviews focus on Digital design & Verilog coding concepts
  • o There are few domains of VLSI like Physical design, STA, GLS which only require strong digital design understanding.
  • Even though we don’t use Analog design concepts much in VLSI functional verification, however it need to be learnt with an eye on interviews.

What to learn

Digital Design learning, please note it is not limited to it.

  • Flipflop FF implementation using NAND gates Setup time, hold time definition and calculation Metastability
  • Latch
  • Counter gray counter ring counter mod counter johnson counter
  • FIFO, how is it used for data flow synchronization, Synchronous FIFO Asynchronous FIFO How handshaking can replace FIFO
  • Race condition
  • Multiplexer Using MUX to create different logic gates
  • Decoder, encoder, priority decoder
  • even, odd parity, CRC : How these are useful in detecting transmission errors
  • Master-slave handshaking
  • Inverter using CMOS
  • Half adder, full adder using half adder
  • truth table for half adder, full adder, multiplexer, counters above
  • buffer usage in digital design, signal drive strength, load, significance
  • PLL, VCO, how clock is generated in real SOC, we don’t use forever logic, we use PLL
  • Generating one clock frequency from exisitng clock Use 100MHz clock to generate 200Mhz Use 100Mhz clock to generate 50MHz
  • T-Flipflop, use in 2 & 3 stage synchronizers
  • Clock domain crossing, use of synchornizers
  • Reset, Asynchronous reset, synchronous reset
  • Moore & Mealy state machine
  • Signed, unsigned numbers, 1’s complement, 2’s complement
  • Karnaugh map, using truth table
  • Octal, hexa, decimal, binary conversions
  • NAND gate or NOR gate as universal gate
  • Memory, different types of memroies
  • rise, fall time, propagration delay, SDF format
  • setup time, hold time calculation for flipflop
  • Fundamentals of STA, PD, Layout, DFT, Post Silicon Validation
  • Basics of Analog circuits, Oscillator, ADC, DAC
  • SDF Annotation, GLS concepts
  • Clock routing using T-branching : keeping all path length same
  • Clock routing using Diasy-chain routing
  • Clock duty cycle and clock jitter Generating clock with 60% duty cycle
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