What are the differences between Active Low Data and Active High Data of 74181?

Discussion in 'General Electronics Chat' started by jcyang, Jan 18, 2010.

  1. jcyang

    Thread Starter New Member

    Jan 18, 2010
    There are two function table for 74181(Arithmetic Logic Unit),one is for Active Low Data,the other is for Active High Data.

    What are the differences?How could one chip own two different suit of functionalities?
    1. If the 74181 chip could recieve Active Low Data or Active High Data,is it dynamically configurable?Or,there are two kind of 74181 chip in the market?
    2. Considering the two function tables,when S3..S0 = LLLL M = L,for Active Low Data the output F = not A,but for Active High Data the output F = not A.So the outputs for the two kinds of input are same.Does it mean the internal architecture of the two chips are not the same.Because if it is,one output F = not A then the other output should be F = A.
  2. Papabravo


    Feb 24, 2006
    Memory chips that were contemporary to the 74181 often read out the complement of what was written into the memory. It offers the possibility of eliminating a set of inverters. It does not know if its inputs are active high or active low. Whatever they are you get the sixteen functions based on that choice.
    moh1967 likes this.