Encoders The inverse function of a decoder

Priority Encoder resolve the ambiguity of illegal inputs only one of the input is encoded D 3 has the highest priority D 0 has the lowest priority X: don't-care conditions V: valid output indicator

Magnitude Comparator The comparison of two numbers outputs: A>B, A=B, A<B Design Approaches the truth table 2 2n entries - too cumbersome for large n use inherent regularity of the problem reduce design efforts reduce human errors

Algorithm -> logic A = A 3 A 2 A 1 A 0 ; B = B 3 B 2 B 1 B 0 A=B if A 3 =B 3, A 2 =B 2, A 1 =B 1 and A 1 =B 1 equality: x i = A i B i +A i 'B i ' (A=B) = x 3 x 2 x 1 x 0 (A>B) = A 3 B 3 '+x 3 A 2 B 2 '+x 3 x 2 A 1 B 1 '+x 3 x 2 x 1 A 0 B 0 ' (A>B) = A 3 'B 3 +x 3 A 2 'B 2 +x 3 x 2 A 1 'B 1 +x 3 x 2 x 1 A 0 'B 0 Implementation x i = (A i B i '+A i 'B i )'