OpenFPGA/yosys/tests/simple/carryadd.v

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module carryadd(a, b, y);
parameter WIDTH = 8;
input [WIDTH-1:0] a, b;
output [WIDTH-1:0] y;
genvar i;
generate
for (i = 0; i < WIDTH; i = i+1) begin:STAGE
wire IN1 = a[i], IN2 = b[i];
wire C, Y;
if (i == 0)
assign C = IN1 & IN2, Y = IN1 ^ IN2;
else
assign C = (IN1 & IN2) | ((IN1 | IN2) & STAGE[i-1].C),
Y = IN1 ^ IN2 ^ STAGE[i-1].C;
assign y[i] = Y;
end
endgenerate
// assert property (y == a + b);
endmodule