CLA4.hdl

/* 
* 4 bit CLA
*/

CHIP CLA4{
    IN x[4] , y[4] , C;
    OUT S[4] , Cn-1;

    PARTS:
    Xor(a = x[0] , b = y[0] , out = P0);
    Xor(a = x[1] , b = y[1] , out = P1);
    Xor(a = x[2] , b = y[2] , out = P2);
    Xor(a = x[3] , b = y[3] , out = P3);

    And(a = x[0] , b = y[0] , out = G0);
    And(a = x[1] , b = y[1] , out = G1);
    And(a = x[2] , b = y[2] , out = G2);
    And(a = x[3] , b = y[3] , out = G3);

    And(a = P0 , b = C , out = Ct1);
    Or(a = Ct1 , b = G0 , out = C1);			// C1 = P0.C + G0

    And3In(a = P1 , b = P0 , c = C, out = Ct2);
    And(a = P1 , b = G0 , out = C2t2);
    OR3IN(a = Ct2 , b = C2t2 , c = G1 , out = C2);	// C2 = P1.P0.C + P1.G0 + G1

    And4In(a = P2 , b = P1 , c = P0 , d = C , out = Ct3);
    And3In(a = P2 , b = P1 , c = G0 , out = C2t3);
    And(a = P2 , b = G1 , out = C3t3);
    OR4IN(a = Ct3 , b = C2t3 , c = C3t3 , d = G2, out = C3);	// C3 = P2.P1.P0.C + P2.P1.G0 + P1.G1 + G2

    Or(a = C3 , b = false , out = Cn-1);

    // S[i] = ( x[i] Xor y[i] ) Xor Ci    (C0 = C)

    Xor(a = x[0] , b = y[0] , out = t10);
    Xor(a = t10 , b = C , out = S[0]);			

    Xor(a = x[1] , b = y[1] , out = t11);
    Xor(a = t11 , b = C1 , out = S[1]);

    Xor(a = x[2] , b = y[2] , out = t12);
    Xor(a = t12 , b = C2 , out = S[2]);

    Xor(a = x[3] , b = y[3] , out = t13);
    Xor(a = t13 , b = C3 , out = S[3]);
}