////////////////////////////////////////////////////////////////////////
//
// Project Reality
//
// module:	bl_add
// description:	Carry-propagating adder for blend unit. 4, 3 bits in,
//		carry in 1 forced, 4 bits out, no carry out.
//
// designer:	Phil Gossett
// date:	8/11/94
//
////////////////////////////////////////////////////////////////////////

module bl_add (a, b, s);

input [3:0] a;
input [2:0] b;

wire [2:0] c;

output [3:0] s;

xn02d1  adds0 (           .a1(a[0]), .a2(b[0]), .zn(s[0]));
or02d1  addc0 (           .a1(a[0]), .a2(b[0]),             .z(c[0]));
ad01d1h adds1 (.ci(c[0]),  .a(a[1]),  .b(b[1]),  .s(s[1]), .co(c[1]));
ad01d1h adds2 (.ci(c[1]),  .a(a[2]),  .b(b[2]),  .s(s[2]), .co(c[2]));
xo02d1h adds3 (.a1(c[2]), .a2(a[3]),             .z(s[3]));

endmodule // bl_add