source: sandbox/MultiChannelUSB/adc_lvds.v

(* ALTERA_ATTRIBUTE = {"{-to int_data_p} DDIO_INPUT_REGISTER=HIGH; {-to int_data_n} DDIO_INPUT_REGISTER=LOW"} *)

module adc_lvds
        #(
                parameter       size    =       8, // number of channels
                parameter       width   =       24 // channel resolution
        )
        (
                input   wire                                            clock,

                input   wire                                            lvds_dco,
                input   wire                                            lvds_fco,
                input   wire    [size-1:0]                      lvds_d,

                output  wire                                            adc_frame,
                output  wire    [size*width-1:0]        adc_data

        );
        localparam      width2  =       width + 2;
                
        reg                                                     state, int_rdreq, adc_frame_reg;
        wire                                            int_wrfull, int_rdempty;

        reg             [size-1:0]                      int_data_p, int_data_n;

        reg     [2:0]                           int_edge_reg;

        reg     [size*width-1:0]        int_fifo_reg;
        wire    [size*width-1:0]        int_fifo_wire;

        reg     [size*width2-1:0]       int_data_reg;
        wire    [size*width2-1:0]       int_data_wire;

        wire    [size*width-1:0]        int_q_wire;
        reg             [size*width-1:0]        adc_data_reg;
        


        genvar j;

        generate
                for (j = 0; j < size; j = j + 1)
                begin : INT_DATA
// MSB first
//                      assign int_data_wire[j*width+width-1:j*width] = {int_data_reg[j*width+width-3:j*width], int_data_p[j], int_data_n[j]};
// LSB first
//                      assign int_data_wire[j*width+width-1:j*width] = {int_data_n[j], int_data_p[j], int_data_reg[j*width+width-1:j*width+2]};
                        assign int_data_wire[j*width2+width2-1:j*width2] = {int_data_n[j], int_data_p[j], int_data_reg[j*width2+width2-1:j*width2+2]};
                        assign int_fifo_wire[j*width+width-1:j*width] = int_data_reg[j*width2+width2-3:j*width2];
                end
        endgenerate

        dcfifo #(
                .intended_device_family("Cyclone III"),
                .lpm_numwords(16),
                .lpm_showahead("ON"),
                .lpm_type("dcfifo"),
                .lpm_width(size*width),
                .lpm_widthu(4),
                .rdsync_delaypipe(4),
                .wrsync_delaypipe(4),
                .overflow_checking("ON"),
                .underflow_checking("ON"),
                .use_eab("ON")) fifo_unit (
//              .data(int_data_wire),
                .data(int_fifo_reg),
                .rdclk(clock),
                .rdreq((~int_rdempty) & int_rdreq),
                .wrclk(lvds_fco),
                .wrreq(~int_wrfull),
                .q(int_q_wire),
                .rdempty(int_rdempty),
                .wrfull(int_wrfull),
                .aclr(),
                .rdfull(),
                .rdusedw(),
                .wrempty(),
                .wrusedw());

        always @ (posedge clock)
        begin
                case (state)
                        1'b0:
                        begin
                                int_rdreq <= 1'b1;
                                adc_frame_reg <= 1'b0;
                                state <= 1'b1;
                        end

                        1'b1: 
                        begin
                                if (~int_rdempty)
                                begin
                                        int_rdreq <= 1'b0;
                                        adc_frame_reg <= 1'b1;
                                        adc_data_reg <= int_q_wire;
                                        state <= 1'b0;
                                end
                        end
                endcase
        end
        
        always @ (negedge lvds_dco)
        begin
                int_data_n <= lvds_d;
        end

        always @ (posedge lvds_dco)
        begin
                int_data_p <= lvds_d;
                int_data_reg <= int_data_wire;
                int_edge_reg <= {(~int_edge_reg[1]), int_edge_reg[0], lvds_fco};
                if (int_edge_reg[1] & int_edge_reg[2])
                begin
                        int_fifo_reg <= int_fifo_wire;
                end
        end

        assign  adc_frame = adc_frame_reg;
        assign  adc_data = adc_data_reg;

endmodule