What is the difference between PLA and ROM?
A read-only memory (ROM) is a logic circuit that can generate all of the possible minterms of its inputs.



So, these are the characteristics of the ROM:


  Input products are hard-wired and
  include all possible minterms. Output
  summation circuitry is programmable.




A field programmable logic array (FPLA) only those minterms that are needed are generated. Also, each is generated only once, even though it may appear multiple times in the output expressions.



So, these are the characteristics of the FPLA:


  Input product circuitry is
  programmable. Output summation
  circuitry is programmable.




A programmable array logic (PAL) has the input circuitry similar to that of the FPLA. However, the output circuitry includes hardwired OR logic and is not programmable.



So, these are the characteristics of the PAL:


  Input product circuitry is
  programmable. Output summation
  circuitry is hardwired.