source: trunk/MultiChannelUSB/oscilloscope.v@ 28

module oscilloscope
        (
                input   wire                    clk, reset,
                input   wire                    data_ready,
                input   wire    [15:0]  raw_data, uwt_data, threshold,
                input   wire    [9:0]   address,
                output  wire    [9:0]   start_address,
                output  wire    [15:0]  q
        );
        
        // signal declaration
        reg             [3:0]   state_reg, state_next;

        reg                             wren_reg, wren_next;
        reg             [9:0]   addr_reg, addr_next;
        reg             [15:0]  data_reg, data_next;

        reg                             trig_reg, trig_next;
        reg             [9:0]   trig_addr_reg, trig_addr_next;
        reg             [9:0]   counter_reg, counter_next;

        wire    [15:0]  q_wire;

        ram1024x16 ram1024x16_unit (
                .clock(~clk),
                .data(data_reg),
                .rdaddress(address),
                .wraddress(addr_reg),
                .wren(wren_reg),
                .q(q_wire));

        // body
        always @(posedge clk)
        begin
                if (reset)
        begin
                        state_reg <= 4'b1;
                end
                else
                begin
                        state_reg <= state_next;
                        wren_reg <= wren_next;
                        addr_reg <= addr_next;
                        data_reg <= data_next;
                        trig_reg <= trig_next;
                        trig_addr_reg <= trig_addr_next;
                        counter_reg <= counter_next;
                end
        end

        always @*
        begin
                state_next = state_reg;
                wren_next = wren_reg;
                addr_next = addr_reg;
                data_next = data_reg;
                trig_next = trig_reg;
                trig_addr_next = trig_addr_reg;
                counter_next = counter_reg;

                case (state_reg)
                        0: ; // nothing to do  
                        1: 
                        begin
                                // start reset
                                wren_next = 1'b1;
                                addr_next = 0;
                                data_next = 0;
                                trig_next = 0;
                                trig_addr_next = 0;
                                counter_next = 0;
                                state_next = 4'd2;
                        end
                        
                        2:
                        begin
                                // write zeros
                                if (&addr_reg)
                                begin
                                        wren_next = 1'b0;
                                        state_next = 4'd3;
                                end
                                else
                                begin
                                        addr_next = addr_reg + 10'd1;
                                end
                        end
        
                        3:
                        begin
                                if (&counter_reg)
                                begin
                                        state_next = 4'd0;
                                end
                                else if (data_ready)
                                begin
                                        // start write
                                        wren_next = 1'b1;
                                        data_next = raw_data;
                                        if ((~trig_reg)
                                                & (counter_reg == 10'd512)
                                                & (uwt_data >= threshold))
                                        begin
                                                // trigger
                                                trig_next = 1'b1;
                                                trig_addr_next = addr_reg;
                                        end
                                        state_next <= 4'd4;
                                end
                        end

                        4:
                        begin
                                // stop write
                                wren_next <= 1'b0;
                                addr_next = addr_reg + 10'd1;
                                if (trig_reg | (counter_reg < 10'd512))
                                begin
                                        counter_next = counter_reg + 10'd1;
                                end
                                state_next = 4'd3;
                        end

                        default:
                        begin
                                state_next = 4'd0;
                        end
                endcase
        end

        // output logic
        assign  q                               =       q_wire;
        assign  start_address   =       trig_reg ? trig_addr_reg ^ 10'h200 : addr_reg + 10'd1;

endmodule