Subversion Repositories pentevo

module pfpzu(
    input oe_n,
        input res_n,
        input [15:2] a,
        output a16,a17
        
);

        reg [1:0] plane;
        reg [1:0] newplane;

        reg enable_switch;



        assign a17 = plane[1];
        assign a16 = plane[0];
        
        
        always @*
        begin
                if( a[15:4] == 12'b100000010000 )
                        enable_switch <= 1;
                else
                        enable_switch <= 0;
        end


        always @*
        begin
                case( {a[3:2],plane[1:0]} )
                4'b0000:
                        newplane <= 0;
                4'b0001:
                        newplane <= 1;
                4'b0010:
                        newplane <= 2;
                4'b0011:
                        newplane <= 3;
                4'b0100:
                        newplane <= 3;
                4'b0101:
                        newplane <= 3;
                4'b0110:
                        newplane <= 3;
                4'b0111:
                        newplane <= 2;
                4'b1000:
                        newplane <= 2;
                4'b1001:
                        newplane <= 2;
                4'b1010:
                        newplane <= 0;
                4'b1011:
                        newplane <= 1;
                4'b1100:
                        newplane <= 1;
                4'b1101:
                        newplane <= 0;
                4'b1110:
                        newplane <= 1;
                4'b1111:
                        newplane <= 0;
                endcase
        end




        always @(posedge oe_n, negedge res_n)
        begin
                if (res_n==1'b0)
                        plane <= 2'b00;
                else    
                if( enable_switch==1 )
                begin
                        plane <= newplane;
                end
        end


endmodule