// -----------------------------------------------------------------------------
//
// Copyright 2013(c) Analog Devices, Inc.
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//  - Use of the software either in source or binary form, must be run
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// -----------------------------------------------------------------------------
// FILE NAME : AD7401.v
// MODULE NAME : AD7401
// AUTHOR :  Adrian Costina
// AUTHOR'S EMAIL : adrian.costina@analog.com
// -----------------------------------------------------------------------------
// KEYWORDS : Analog Devices, Motor Control, AD7401
// -----------------------------------------------------------------------------
// PURPOSE : Driver for 
// -----------------------------------------------------------------------------
// REUSE ISSUES
// Reset Strategy      : Active high reset signal
// Clock Domains       : fpga_clk_i, 100 MHz
//                       adc_clk_i, up to 20 MHz
// Critical Timing     : N/A
// Test Features       : N/A
// Asynchronous I/F    : N/A
// Instantiations      : N/A
// Synthesizable (y/n) : Y
// Target Device       :
// Other               :
// -----------------------------------------------------------------------------
// -----------------------------------------------------------------------------

`timescale 1 ns / 100 ps //Use a timescale that is best for simulation.

//------------------------------------------------------------------------------
//----------- Module Declaration -----------------------------------------------
//------------------------------------------------------------------------------

module ad7401
//----------- Ports Declarations -----------------------------------------------
(
    //clock and reset signals
    input               fpga_clk_i,     // system clock
    input               adc_clk_i,      // up to 20 MHZ clock
    input               reset_i,        // active high reset signal

    //IP control and data interface
    output reg  [15:0]  data_o,          // data read from the ADC
    output reg          data_rd_ready_o, // when set to high the data read from the ADC is available on the data_o bus
    output reg          adc_status_o,

    //AD7401 control and data interface
    input               adc_mdata_i    // AD7401 MDAT pin
);

//------------------------------------------------------------------------------
//----------- Wire Declarations ------------------------------------------------
//------------------------------------------------------------------------------

wire        data_rdy_s;
wire [15:0] data_s ;

//------------------------------------------------------------------------------
//----------- Registers Declarations -------------------------------------------
//------------------------------------------------------------------------------
//State machine
reg [3:0]   present_state;
reg [3:0]   next_state;

reg         data_rdy_s_d1;
reg         data_rdy_s_d2;

//------------------------------------------------------------------------------
//----------- Local Parameters -------------------------------------------------
//------------------------------------------------------------------------------

//States
localparam WAIT_DATA_RDY_HIGH_STATE = 4'b0001;
localparam ACQUIRE_DATA_STATE       = 4'b0010;
localparam TRANSFER_DATA_STATE      = 4'b0100;
localparam WAIT_DATA_RDY_LOW_STATE  = 4'b1000;

//------------------------------------------------------------------------------
//----------- Assign/Always Blocks ---------------------------------------------
//------------------------------------------------------------------------------

// synchronize data on fpga_clki
always @(posedge fpga_clk_i)
begin
    data_rdy_s_d1 <= data_rdy_s;
    data_rdy_s_d2 <= data_rdy_s_d1;
end

always @(posedge fpga_clk_i)
begin
    if(reset_i == 1'b1)
    begin
        present_state      <= WAIT_DATA_RDY_HIGH_STATE;
        adc_status_o       <= 1'b0;
    end
    else
    begin
        present_state <= next_state;
        case (present_state)
            WAIT_DATA_RDY_HIGH_STATE:
            begin
                data_rd_ready_o  <= 1'b0;
            end
            ACQUIRE_DATA_STATE:             // Acquire data from the filter
            begin
                data_o          <= data_s;
                data_rd_ready_o <= 1'b0;
                adc_status_o    <= 1'b1;
            end
            TRANSFER_DATA_STATE:            // Transfer data to the upper module to write in memory
            begin
                data_rd_ready_o <= 1'b1;
            end
            WAIT_DATA_RDY_LOW_STATE:
            begin
                data_rd_ready_o <= 1'b0;
            end
        endcase
    end
end

always @(present_state, data_rdy_s_d2)
begin
    next_state <= present_state;
    case (present_state)
        WAIT_DATA_RDY_HIGH_STATE:
        begin
            if(data_rdy_s_d2 == 1'b1)
            begin
                next_state  <= ACQUIRE_DATA_STATE;
            end
        end
        ACQUIRE_DATA_STATE:
        begin
            next_state      <= TRANSFER_DATA_STATE;
        end
        TRANSFER_DATA_STATE:
        begin
            next_state      <= WAIT_DATA_RDY_LOW_STATE;
        end
        WAIT_DATA_RDY_LOW_STATE:
        begin
            if(data_rdy_s_d2 == 1'b0)
            begin
                next_state  <= WAIT_DATA_RDY_HIGH_STATE;
            end
        end
        default:
        begin
            next_state      <= WAIT_DATA_RDY_HIGH_STATE;
        end
    endcase
end

dec256sinc24b filter(
    .mclkout_i(adc_clk_i),
    .reset_i(reset_i),
    .mdata_i(adc_mdata_i),
    .data_rdy_o(data_rdy_s),
    .data_o(data_s));

endmodule