//////////////////////////////////////////////////////////////////////
////                                                              ////
//// WISHBONE SD Card Controller IP Core                          ////
////                                                              ////
//// sd_data_xfer_trig.v                                          ////
////                                                              ////
//// This file is part of the WISHBONE SD Card                    ////
//// Controller IP Core project                                   ////
//// http://opencores.org/project,sd_card_controller              ////
////                                                              ////
//// Description                                                  ////
//// Module resposible for triggering data transfer based on      ////
//// command transfer completition code                           ////
////                                                              ////
//// Author(s):                                                   ////
////     - Marek Czerski, ma.czerski@gmail.com                    ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
////                                                              ////
//// Copyright (C) 2013 Authors                                   ////
////                                                              ////
//// This source file may be used and distributed without         ////
//// restriction provided that this copyright statement is not    ////
//// removed from the file and that any derivative work contains  ////
//// the original copyright notice and the associated disclaimer. ////
////                                                              ////
//// This source file is free software; you can redistribute it   ////
//// and/or modify it under the terms of the GNU Lesser General   ////
//// Public License as published by the Free Software Foundation; ////
//// either version 2.1 of the License, or (at your option) any   ////
//// later version.                                               ////
////                                                              ////
//// This source is distributed in the hope that it will be       ////
//// useful, but WITHOUT ANY WARRANTY; without even the implied   ////
//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR      ////
//// PURPOSE. See the GNU Lesser General Public License for more  ////
//// details.                                                     ////
////                                                              ////
//// You should have received a copy of the GNU Lesser General    ////
//// Public License along with this source; if not, download it   ////
//// from http://www.opencores.org/lgpl.shtml                     ////
////                                                              ////
//////////////////////////////////////////////////////////////////////
`include "sd_defines.v" 

module sd_data_xfer_trig (
           input sd_clk,
           input rst,
           input cmd_with_data_start_i,
           input r_w_i,
           input [`INT_CMD_SIZE-1:0] cmd_int_status_i,
           output reg start_tx_o,
           output reg start_rx_o
       );

reg r_w_reg;
parameter SIZE = 2;
reg [SIZE-1:0] state;
reg [SIZE-1:0] next_state;
parameter IDLE             = 2'b00;
parameter WAIT_FOR_CMD_INT = 2'b01;
parameter TRIGGER_XFER     = 2'b10;

always @(state or cmd_with_data_start_i or r_w_i or cmd_int_status_i)
begin: FSM_COMBO
    case(state)
        IDLE: begin
            if (cmd_with_data_start_i & r_w_i)
                next_state <= TRIGGER_XFER;
            else if (cmd_with_data_start_i)
                next_state <= WAIT_FOR_CMD_INT;
            else
                next_state <= IDLE;
        end
        WAIT_FOR_CMD_INT: begin
            if (cmd_int_status_i[`INT_CMD_CC])
                next_state <= TRIGGER_XFER;
            else if (cmd_int_status_i[`INT_CMD_EI])
                next_state <= IDLE;
            else
                next_state <= WAIT_FOR_CMD_INT;
        end
        TRIGGER_XFER: begin
            next_state <= IDLE;
        end
        default: next_state <= IDLE;
    endcase
end

always @(posedge sd_clk or posedge rst)
begin: FSM_SEQ
    if (rst) begin
        state <= IDLE;
    end
    else begin
        state <= next_state;
    end
end

always @(posedge sd_clk or posedge rst)
begin
    if (rst) begin
        start_tx_o <= 0;
        start_rx_o <= 0;
        r_w_reg <= 0;
    end
    else begin
        case(state)
            IDLE: begin
                start_tx_o <= 0;
                start_rx_o <= 0;
                r_w_reg <= r_w_i;
            end
            WAIT_FOR_CMD_INT: begin
                start_tx_o <= 0;
                start_rx_o <= 0;
            end
            TRIGGER_XFER: begin
                start_tx_o <= ~r_w_reg;
                start_rx_o <= r_w_reg;
            end
        endcase
    end
end

endmodule