Encoders/Decoders

• This is Carpinelli, chapter 3.1
• A deoder has
  • n input bits.
  • 2ⁿ output bits.
  • The output lines are numbered 0 through 2ⁿ-1
  • Possibly an eanble
• The line corresponding to the input value is lit. (Only one line)
• If the enable is present, then the circuit is active.
• These are really quite simple.
  • We need an and gate for each possible output.
  • We just build the proper "logic" for the named minterm.
  • But possibly an additional input for the enable button.
  • 
• I am building 2 input bit decoders just for simplicity.
• Using the enable, we can extend these indefinately
  • 
• An encoder does the opposite
  • n, n = 2^{k input bits, only one active at a time.}
  • possibly an enable bit
  • k output bits.
  • They represent the binary code for the line that is active.
  • 
• These need to be in the same directory