Monday, November 17, 2008

Basic Digital Interview Questions

What is the function of a D flip-flop, whose inverted output is connected to its input ?


Design a circuit to divide input frequency by 2.


Design a divide-by-3 sequential circuit with 50% duty cycle.


Design a divide-by-5 sequential circuit with 50% duty cycle.


What are the different types of adder implementations ?


Draw a Transmission Gate-based D-Latch.


Give the truth table for a Half Adder. Give a gate level implementation of it.

Design an XOR gate from 2:1 MUX and a NOT gate


What is the difference between a LATCH and a FLIP-FLOP ?


* Latch is a level sensitive device while flip-flop is an edge sensitive device.
* Latch is sensitive to glitches on enable pin, whereas flip-flop is immune to glitches.
* Latches take less gates (also less power) to implement than flip-flops.
* Latches are faster than flip-flops.

Design a D Flip-Flop from two latches.

Design a 2 bit counter using D Flip-Flop.

What are the two types of delays in any digital system ?

Design a Transparent Latch using a 2:1 Mux.

Design a 4:1 Mux using 2:1 Muxes and some combo logic.

What is metastable state ? How does it occur ?


What is metastability ?


Design a 3:8 decoder


Design a FSM to detect sequence "101" in input sequence.


Convert NAND gate into Inverter, in two different ways.


Design a D and T flip flop using 2:1 mux; use of other components not allowed, just the mux.


Design a divide by two counter using D-Latch.


Design D Latch from SR flip-flop.


Define Clock Skew , Negative Clock Skew, Positive Clock Skew.


What is Race Condition ?


Design a 4 bit Gray Counter.


Design 4-bit Synchronous counter, Asynchronous counter.


Design a 16 byte Asynchronous FIFO.


What is the difference between an EEPROM and a FLASH ?


What is the difference between a NAND-based Flash and a NOR-based Flash ?


You are given a 100 MHz clock. Design a 33.3 MHz clock with and without 50&37; duty cycle.


Design a Read on Reset System ?


Which one is superior: Asynchronous Reset or Synchronous Reset ? Explain.


Design a State machine for Traffic Control at a Four point Junction.


What are FIFO's? Can you draw the block diagram of FIFO? Could you modify it to make it asynchronous FIFO ?


How can you generate random sequences in digital circuits?

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