1. Cascading 1-Bit Comparators
Discussion D7.0

2. A 1-Bit Comparator
The variable Gout is 1 if Gin = 1 or if Ein = 1 and x > y.
The variable Eout is 1 if Ein = 1 and x = y.

3. module comp4 ( x, y, gt, eq, lt );
input [3:0] x ;
wire [3:0] x ;
input [3:0] y ;
wire [3:0] y ;
output lt ;
wire lt ;
output gt ;
wire gt ;
output eq ;
wire eq ;
A 4-Bit Comparator x y lt

4. A 4-Bit Comparator wire [4:0] G; wire [4:0] E; assign G[4] = 0;lt
wire [4:0] G;
wire [4:0] E;
assign G[4] = 0;
assign E[4] = 1;
assign gt = G[0];
assign eq = E[0];
assign lt = ~(G[0] | E[0]);

5. comp1bit U3(.xi(x[3]) ,.yi(y[3]) ,.Ein(E[4]) ,
.Eout(E[3]) ,.Gin(G[4]) ,.Gout(G[3]) );

6. comp1bit U3(.xi(x[3]) ,.yi(y[3]) ,.Ein(E[4]) ,
.Eout(E[3]) ,.Gin(G[4]) ,.Gout(G[3]) );

7. comp1bit U3(. xi(x[3]) ,. yi(y[3]) ,. Ein(E[4]) ,. Eout(E[3]) ,
comp1bit U3(.xi(x[3]) ,.yi(y[3]) ,.Ein(E[4]) ,.Eout(E[3]) , .Gin(G[4]) ,.Gout(G[3]) );
comp1bit U2(.xi(x[2]) ,.yi(y[2]) ,.Ein(E[3]) ,.Eout(E[2]) , .Gin(G[3]) ,.Gout(G[2]) );
comp1bit U1(.xi(x[1]) ,.yi(y[1]) ,.Ein(E[2]) ,.Eout(E[1]) , .Gin(G[2]) ,.Gout(G[1]) );
comp1bit U0(.xi(x[0]) ,.yi(y[0]) ,.Ein(E[1]) ,.Eout(E[0]) , .Gin(G[1]) ,.Gout(G[0]) );
endmodule