triangle

module triangle (clk, reset, nt, xi, yi, busy, po, xo, yo);
input clk, reset, nt;
input [2:0] xi, yi;
output reg busy, po;
output [2:0] xo, yo;

reg [2:0] X[2:0];
reg [2:0] Y[2:0];
reg [2:0] X_ptr, Y_ptr;
reg [3:0] state;

wire [7:0] r1, r2;

assign xo = X_ptr;
assign yo = Y_ptr;

assign  r1=(X_ptr-X[0]+3'h1)*(Y[2]-Y[0]);
              // x1 - (x + 1)
assign  r2=(X[2]-X[0])*(Y_ptr - Y[0]);

always@(posedge clk or posedge reset) begin
    if(reset) begin
        {X[2],X[1],X[0]} <= 9'h0;
        {Y[2],Y[1],Y[0]} <= 9'h0;
        busy <= 1'h0;
        po <= 1'h0;
        X_ptr <= 3'h0;
        Y_ptr <= 3'h0;
        state <= 4'h0;
    end

    else begin
        case(state)
        4'h0:
        begin
            if(nt) begin
                X[0] <= xi;
                Y[0] <= yi;
                X_ptr <= xi[0];
                Y_ptr <= yi[0];
                busy <= 1'h1;
                state <= 4'h1;
            end
        end

        4'h1:
        begin
            X[1] <= xi;
            Y[1] <= yi;
            state <= 4'h2;
        end

        4'h2:
        begin
            X[2] <= xi;
            Y[2] <= yi;
            po <= 1'h1;
            state <= 4'h3;
        end

        4'h3:
        begin
            if( (X_ptr==X[2]) & (Y_ptr==Y[2]))
            begin
                state <= 4'h4;
                po <= 1'h0;
            end

            else if (X_ptr == X[1])
            begin
                po <= 1'h0;
                X_ptr <= X[0];
                Y_ptr <= Y_ptr+3'h1;
            end

            else
            begin
                po <= (r1 >= r2)?1'h1:1'h0; // if the point is now locate at left of scale
                X_ptr <= X_ptr+3'h1;
            end
        end

        4'h4:
        begin
            busy <= 1'h0;
            state <= 4'h0;
        end

        endcase
    end
end
endmodule