ROM vs. PLA

• ROM approach advantageous when

  • design time is short (no need to minimize output functions)
  • most input combinations are needed (e.g., code converters)
  • little sharing of product terms among output functions

• ROM problems

  • size doubles for each additional input
  • can't exploit don't cares

• PLA approach advantageous when

  • design tools are available for multi-output minimization
  • there are relatively few unique minterm combinations
  • many minterms are shared among the output functions

• PAL problems

  • constrained fan-ins on OR plane

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