// --------------------------------------------

// module multiplier_unit_4   multiplier_unit_5  multiplier_quick_add_4     multiplier_quick_add_5

// file name: multiplier_unit.v

// purpose: full addr   

// author Hejun 

// simulate Modelsim

//------------------------------------------

// Revision List

// version 1.0



`timescale 	 1ns/1ns


module multiplier_unit_4(
    y,
    x,
    shiftin,
    shiftout,
    cin,
    cout,
    pp
    );
 

input [3:0] y;
input [3:0] x;
//input shiftin1;
input [1:0] shiftin;
output [3:0] shiftout;
input cin;
output [3:0] pp;
output cout;
//output cout2;
//output c;

wire [3:0] shiftout;
wire [3:0] pp;
wire k;
wire w;
wire p1;
wire p2;
wire [3:0] t1;
wire [3:0] t2;
wire [3:0] t3;
wire [3:0] t4;
wire c;
wire cout;

//wire cout2;

assign k = y[3] & y[2] & y[1] & y[0] | ~y[3] & ~y[2] & ~y[1] & ~y[0];
assign w = y[0] ? ~y[1] : y[1];
assign p1 = y[3] ? ~y[2] : y[2];
assign p2 = y[2] ? ~y[1] : y[1];
  
assign shiftout[3:0] = ~(x[3:0]^{y[3],y[3],y[3],y[3]});

assign t1[3:0] = w ? shiftout[3:0] : {shiftout[2:0],shiftin[1]};
assign t2[3:0] = w ? {shiftout[2:0],shiftin[1]} : {shiftout[1:0],shiftin[1:0]};


assign t3[3:0] = (w & ~p1) ? t1[3:0] : 4'bz; //x
//assign t3 = (w & p1) ? ((~(~t2 ^ ~shiftout)) & ~y[3]) | ((t2 ^ shiftout) & y[3]):'bz;
assign t3 = (~w & p2) ? t1 : 4'bz;    //2x
assign t3 = (~w & ~p2) ? t2 : 4'bz;  //4x
assign t3 = (w & p1) ? (~t4[3:0] & {~y[3],~y[3],~y[3],~y[3]}) | (t4[3:0] & {y[3],y[3],y[3],y[3]}): 4'bz;    //3x


multiplier_quick_add_4      multiplier_quick_add_4_1(
      .a                        ((shiftout & {y[3],y[3],y[3],y[3]})|(~shiftout & {~y[3],~y[3],~y[3],~y[3]})),
      .b                        (({shiftout[2:0],shiftin[1]} & {y[3],y[3],y[3],y[3]})|({~shiftout[2:0],~shiftin[1]} & {~y[3],~y[3],~y[3],~y[3]})),
      .cin                      (cin),
      .s                        (t4),
      .cout                     (c)
      );


assign pp[3:0] = k? 4'b0 : ~t3[3:0];

assign cout =(w & p1) ? c : 1'b0;


//assign sumout = ((sumin &  ^ cin1  ^ pp) & ~y[3]) | ((~(sumin ^ cin1  ^ ~pp)) & y[3]);



endmodule 

module multiplier_full_add(
    a,
    b,
    cin,
    s,
    cout
    );
 
 
input a;
input b;
input cin;
output s;
output cout;

wire s;
wire cout;


assign s = a ^ b ^ cin;
assign cout = ((a ^ b) & cin) | (~(a ^ b) & a);  

endmodule


module multiplier_quick_add_4(
   a,
   b,
   cin,
   s,
   cout
 );


input [4:1] a;
input [4:1] b;
input cin;
output [4:1] s;
output cout;

wire [4:1] s;
wire cout;


wire [4:1] p;
wire [4:1] g;
wire [4:0] c;

assign g[4:1] = a[4:1] & b[4:1];
assign p[4:1] = a[4:1] | b[4:1];

assign c[0] = cin;
assign c[1] = g[1] | p[1] & cin;
assign c[2] = g[2] | p[2] & g[1] | p[2] & p[1] & cin;
assign c[3] = g[3] | p[3] & g[2] | p[3] & p[2] & g[1] | p[3] & p[2] & p[1] & cin ;
assign c[4] = g[4] | p[4] & g[3] | p[4] & p[3] & g[2] | p[4] & p[3] & p[2] & g[1] | p[4] & p[3] & p[2] & p[1] & cin;  

assign s[4:1] = a[4:1] ^ b[4:1] ^ c[3:0];
assign cout = c[4];

endmodule




module multiplier_quick_add_5(
   a,
   b,
   cin,
   s,
   cout
 );


input [5:1] a;
input [5:1] b;
input cin;
output [5:1] s;
output cout;

wire [5:1] s;
wire cout;


wire [5:1] p;
wire [5:1] g;
wire [5:0] c;

assign g[5:1] = a[5:1] & b[5:1];
assign p[5:1] = a[5:1] | b[5:1];

assign c[0] = cin;
assign c[1] = g[1] | p[1] & cin;
assign c[2] = g[2] | p[2] & g[1] | p[2] & p[1] & cin;
assign c[3] = g[3] | p[3] & g[2] | p[3] & p[2] & g[1] | p[3] & p[2] & p[1] & cin ;
assign c[4] = g[4] | p[4] & g[3] | p[4] & p[3] & g[2] | p[4] & p[3] & p[2] & g[1] | p[4] & p[3] & p[2] & p[1] & cin; 
assign c[5] = g[5] | p[5] & g[4] | p[5] & p[4] & g[3] | p[5] & p[4] & p[3] & g[2] | p[5] & p[4] & p[3] & p[2] & g[1] | p[5] & p[4] & p[3] & p[2] & p[1] & cin;


assign s[5:1] = a[5:1] ^ b[5:1] ^ c[4:0];
assign cout = c[5];

endmodule