CS 140 Lecture 6 Professor CK Cheng Tuesday 10/15/02
Part I. Combinational Logic –Implementation K-map Quine-McCluskey
Quine-McCluskey Method Given F R D find min sum of products 1)Exploit the adjacency to find primes 2)Prime implicant chart
Example Id a b c d f (a,b,c,d) Given f(a,b,c,d) w/ F = m(0,1,2,8,14) D = m(9,10)
Corresponding 4-variable K-map f (a, b, c, d) = b’c’ + b’d’ + acd’ d a c b
Using Quine-McCluskey 1)Draw truth table that only include F and D. Order by The number of ones. Divide by regions. Id a a b b c c d d f f I II III IV
Continue again, pairing up rows from adjacent regions if they differ by exactly one bit. Put a dash where they do differ. (0,1) (0,2) (0,8) (1,9) (2,10) (8,9) (8,10) (10,14) a a b b c c d d I&II II&III III&IV
Continuing again. We stop when we can no longer combine rows. We make sure that we cover the entire onset. (0,1,8,9) (0,2,8,10) (10,14) a--1a--1 b00-b00- c0-1c0-1 d-00d-00 Primes m(0,1,8,9) m(0,2,8,10) m(10,14) From here we can draw out the prime implicant chart. The top part corresponds to the onset, the side is the primes we have. Circle essential. m(0,1,8,9) m(0,2,8,10) m(10,14) m0 X m1 X m2 X m8 X m14 X f(a,b,c,d) = m(0,1,8,9) + m(0,2,8,10) + m(10,14) f (a,b,c,d) = b’c’ + b’d’ + acd’
Another example Id a b c d f (a,b,c,d) Given f(a,b,c,d) w/ F = m(0,2,4,7,8,15) D = m(9,12)
Id a a b b c c d d I II III IV V (0,2) (0,4) (0,8) (4,12) (8,9) (8,12) (7,15) a a b b c c d d (0,4,8,12) m(0,2) m(7,15) m(0,4,8,12) m0 X m2 X m4 X m7 X m8 X m15 X f(a,b,c,d) = m(0,2) + m(0,4,8,12) + m(7,15) f (a,b,c,d) = a’b’d + bcd + c’d’