source: trunk/MultiChannelUSB/shift.v@ 166

module shift
        #(
                parameter       shift   =       24, // right shift of the result
                parameter       width   =       27, // bit width of the input data
                parameter       widthr  =       12 // bit width of the output data
        )
        (
                input   wire                                    clock, frame, reset,
                input   wire    [5:0]                   amp_data,
                input   wire    [width-1:0]             inp_data,
                output  wire    [widthr-1:0]    out_data
        );

        localparam      widthp  =       width + 6;

        reg             [5:0]                   amp_data_reg;
        reg             [width-1:0]             inp_data_reg;
        reg             [widthr-1:0]    out_data_reg;
        wire    [widthr-1:0]    out_data_wire;
        wire    [widthp-1:0]    mul_data_wire;
                                                                                                                         
        assign out_data_wire = mul_data_wire[shift+widthr-1:shift]
                + {{(widthr-1){mul_data_wire[widthp-1]}}, mul_data_wire[shift-1]};

        lpm_mult #(
                .lpm_hint("MAXIMIZE_SPEED=9"),
                .lpm_representation("UNSIGNED"),
                .lpm_type("LPM_MULT"),
                .lpm_pipeline(3),
                .lpm_widtha(width),
                .lpm_widthb(6),
                .lpm_widthp(widthp)) mult_unit (
                .clock(clock),
                .clken(1'b1),
                .dataa(inp_data_reg),
                .datab(amp_data_reg),
                .result(mul_data_wire));

        always @(posedge clock)
        begin
                if (reset)
        begin
                        amp_data_reg <= 6'b0;
                        inp_data_reg <= {(width){1'b0}};
                        out_data_reg <= {(widthr){1'b0}};
                end
                else if (frame)
                begin                                   
                        amp_data_reg <= amp_data;
                        inp_data_reg <= inp_data;
                        out_data_reg <= out_data_wire;             
                end             
        end
        

        assign out_data = out_data_reg;

endmodule