// Automatic transmit/receive switching of control pins to daughterboards
// Store everything in registers for now, but could use a RAM for more
// complex state machines in the future

module atr_controller16
  (input clk_i, input rst_i,
   input [5:0] adr_i, input [1:0] sel_i, input [15:0] dat_i, output reg [15:0] dat_o,
   input we_i, input stb_i, input cyc_i, output reg ack_o,
   input run_rx, input run_tx, input [31:0] master_time,
   output [31:0] ctrl_lines);
   
   reg [3:0] state;
   reg [31:0] atr_ram [0:15];  // DP distributed RAM

   wire [3:0] sel_int = { (sel_i[1] & adr_i[1]), (sel_i[0] & adr_i[1]),
			  (sel_i[1] & ~adr_i[1]), (sel_i[0] & ~adr_i[1]) };
   
   // WB Interface
   always @(posedge clk_i)
     if(we_i & stb_i & cyc_i)
       begin
	  if(sel_int[3])
	    atr_ram[adr_i[5:2]][31:24] <= dat_i[15:8];
	  if(sel_int[2])
	    atr_ram[adr_i[5:2]][23:16] <= dat_i[7:0];
	  if(sel_int[1])
	    atr_ram[adr_i[5:2]][15:8] <= dat_i[15:8];
	  if(sel_int[0])
	    atr_ram[adr_i[5:2]][7:0] <= dat_i[7:0];
       end // if (we_i & stb_i & cyc_i)

   always @(posedge clk_i)
     dat_o <= adr_i[1] ? atr_ram[adr_i[5:2]][31:16] : atr_ram[adr_i[5:2]][15:0];
   
   always @(posedge clk_i)
     ack_o <= stb_i & cyc_i & ~ack_o;

   // Control side of DP RAM
   assign     ctrl_lines = atr_ram[state];

   // Put a more complex state machine with time delays and multiple states here
   //  if daughterboard requires more complex sequencing
   localparam ATR_IDLE = 4'd0;
   localparam ATR_TX = 4'd1;
   localparam ATR_RX = 4'd2;
   localparam ATR_FULL_DUPLEX = 4'd3;
   
   always @(posedge clk_i)
     if(rst_i)
       state <= ATR_IDLE;
     else
       case ({run_rx,run_tx})
	 2'b00 : state <= ATR_IDLE;
	 2'b01 : state <= ATR_TX;
	 2'b10 : state <= ATR_RX;
	 2'b11 : state <= ATR_FULL_DUPLEX;
       endcase // case({run_rx,run_tx})
   
endmodule // atr_controller16