module mux4in8b 
title '4-input, 8-bit wide multiplexer PLD 
J. Wakerly, Stanford University' 

" Input and output pins 
!G                               pin;              " Output enable for Y bus
S1..S0                           pin;              " Select inputs, 0-3 ==> A-D
A1..A8, B1..B8, C1..C8, D1..D8   pin;              " 8-bit input buses A, B, C, D
Y1..Y8                           pin istype 'com'; " 8-bit three-state output bus

" Sets
SEL = [S1..S0];
A = [A1..A8];
B = [B1..B8];
C = [C1..C8];
D = [D1..D8];
Y = [Y1..Y8];

equations

"Y.OE = G;
WHEN (SEL == 0) THEN Y = A;
ELSE WHEN (SEL == 1) THEN Y = B;
ELSE WHEN (SEL == 2) THEN Y = C;
ELSE WHEN (SEL == 3) THEN Y = D;

end mux4in8b