/************************************************************************\
|                                                                        |
|               Copyright (C) 1994, Silicon Graphics, Inc.               |
|                                                                        |
|  These coded instructions, statements, and computer programs  contain  |
|  unpublished  proprietary  information of Silicon Graphics, Inc., and  |
|  are protected by Federal copyright  law.  They  may not be disclosed  |
|  to  third  parties  or copied or duplicated in any form, in whole or  |
|  in part, without the prior written consent of Silicon Graphics, Inc.  |
|                                                                        |
\************************************************************************/

// initial ai_controller.v 1.2 Tue Sep 27 22:38:24 PDT 1994 rhn
// $Id: ai_controller.v,v 1.7 2003/01/22 23:24:00 berndt Exp $

// 10/10/94, debug stuff removed, rhn
// 10/27/94, moved full flag to lsb of status reg, rhn
// 12/01/94, added synchronizers
// 12/07/94, flipped abus_word left-right meaning
// 12/10/94, dma_address structure changes for simulation reset, kmh
// 12/11/94, used reset_l to get to resetable flops, kmh
// 12/12/94, length state machine rewrite

module ai_controller(
	clk,
	reset_l,
	dma_grant,
	dma_start,
	reg_write_data,
	reg_address,
	reg_write_enable,
	abus_word,
	test_data,
	dbus_data,
	dma_request,		// outputs
	dma_address,
	reg_read_data,
	bit_rate_reg,
	dac_rate_reg,
	current_sample,
	interrupt_flag
	);

  `include "ai.vh"

  input clk;                                   // system clock
  input reset_l;                               // system reset

  input dma_grant;                             // grant the DMA operation
  input dma_start;                             // start the DMA operation
  input [31:0] reg_write_data;   // register write data from cbus
  input [AI_REG_ADDRESS_SIZE-1:0] reg_address; // register read/write address
  input reg_write_enable;                      // register write enable
  input	abus_word;			       // input sample clock
  input [DBUS_DATA_SIZE-1:0] dbus_data;        // DMA bus

  input [15:0] test_data;
  
  output dma_request;                          // request a DMA read cycle
  output [DRAM_ADDRESS_SIZE-1:0] dma_address;  // DMA slave address
  output [31:0] reg_read_data;   // register read data to cbus

  output [BIT_RATE_SIZE-1:0]	bit_rate_reg;	// dac clk rate
  output [DAC_RATE_SIZE-1:0]	dac_rate_reg;	// dac sample rate
  output [SAMPLE_WORD_SIZE-1:0]	current_sample;	// current 2*16 bit sample
  output interrupt_flag;			// 
  
  // input/output registers
  reg dma_request;

  //  internal fifo control set-reset flags
  reg length2_loaded_flag;		// both length registers are in use
  reg length_zero;
  reg dfifo2_loaded_flag;		// both dma data regs are in use
  reg data_available_flag;		// dma data is available
  reg word_select;			// which half of dma data to use
  reg interrupt_flag;			// 

  // internal registers
  reg dma_busy;
  reg dma_enable;
  reg [31:0] reg_read_data;
  reg [31:0] status_data;
  reg [DRAM_ADDRESS_SIZE-1:0] next_dma_address;
  reg [DRAM_ADDRESS_SIZE-1:0] dma_address;
  reg [LENGTH_COUNT_SIZE-1:0] length_reg;
  reg [LENGTH_COUNT_SIZE-1:0] next_dma_length;
  reg [DBUS_DATA_SIZE-1:0] audio_data;
  reg [DBUS_DATA_SIZE-1:0] next_data;
  reg	[3:0]	bit_rate_reg;
  reg	[DAC_RATE_SIZE-1:0] dac_rate_reg;
  reg	[31:0]	current_sample;
  reg abus_word1;		
  reg abus_word2;		// pipeline reg for syncronization
  reg abus_word3;		// pipeline reg for edge detection
  reg addr_carry_flag;		// carry flag for split dma_address
  reg state;

  // psuedo regs
  reg [DRAM_ADDRESS_SIZE-1:13] adrs_upr ;
  reg [12:3] adrs_lwr;
  reg adrs_lwr_cout;
  reg adrs_inc_lwr;
  reg adrs_load;

  // state machine defines
  parameter
     STATE_IDLE           = 1'd0,
     STATE_READ           = 1'd1;

  // sync flops
  always @(posedge clk) begin
     abus_word1 <= abus_word;
     abus_word2 <= abus_word1;
     abus_word3 <= abus_word2;
  end

  // length == 0 comparitor
  always @(length_reg) begin
    length_zero = (length_reg == 0);
  end

  //synopsys translate_off
  // reg monitor;
  // initial monitor = $test$plusargs("ai_mon");
  //synopsys translate_on

  // test display
  // always @( negedge clk ) begin
    // $display("%b %h %h - %b %h %b %b %b - %b %h %b %h - %b %b %b %h ",
      // length2_loaded_flag, next_dma_length, length_reg,
      // dma_enable, state,
      // dma_request, dma_grant, dma_start,
      // dfifo2_loaded_flag, next_data,
      // data_available_flag, audio_data,
      // abus_word2, abus_word3, word_select, current_sample
      // );
  // end
  // always @( negedge clk ) begin
    //$display("%b %h %h - %b %b",
      //length2_loaded_flag, next_dma_length, length_reg,
      //state, dma_start,
      //);
  //end

  // length register fifo state machine rewrite

  reg [DRAM_ADDRESS_SIZE-1:0] dma_address_temp;
  reg [LENGTH_COUNT_SIZE-1:0] length_reg_temp;
  reg length2_loaded_flag_temp;
  reg interrupt_flag_temp;
  reg addr_carry_flag_temp;

  // combinatoric logic
  always @(	dma_address or
		next_dma_address or 
		length_reg or
		next_dma_length or
		length_zero or 
		length2_loaded_flag or
		addr_carry_flag or
		interrupt_flag or
		reg_write_enable or
		reg_address or
		state or
		dma_start or
		bit_rate_reg
		) begin

	// pre-init to prevent latches from being generated
	length_reg_temp			= length_reg;
	length2_loaded_flag_temp	= length2_loaded_flag;
	interrupt_flag_temp		= interrupt_flag;
	addr_carry_flag_temp		= addr_carry_flag;
	dma_address_temp[DRAM_ADDRESS_SIZE-1:3] 
			= dma_address[DRAM_ADDRESS_SIZE-1:3];
	dma_address_temp[2:0]		= 3'b0;

	if ( length2_loaded_flag == 0 ) begin
	  if ( reg_write_enable == 1 && reg_address == AI_LENGTH_REG ) begin
	      length2_loaded_flag_temp	= 1;
	  end
	end
	else begin
	  if ( length_zero ) begin
              length2_loaded_flag_temp	= 0;
	  end
	end

        if ( reg_write_enable && ( reg_address == AI_STATUS_REG ) &&
	    (interrupt_flag == 1) ) begin
          interrupt_flag_temp	= 0;
	  // $display("interrupt off %d", $time);
        end

	if ( length_zero ) begin
          if ( length2_loaded_flag == 1 ) begin
            length_reg_temp		= next_dma_length;
	    dma_address_temp[DRAM_ADDRESS_SIZE-1:3]
			 = next_dma_address[DRAM_ADDRESS_SIZE-1:3];
            // length2_loaded_flag_temp	= 0; // set in another block
 
	    if (interrupt_flag == 0) begin
              interrupt_flag_temp	= 1;
	      // $display("interrupt on %d", $time);
	    end
          end
	end
	else begin					// length_reg != 0
          if ( state == STATE_READ && dma_start == 1 ) begin
	    // got DMA data 
	    // decrement length & increment address
	    length_reg_temp	= length_reg - 1;
	    { addr_carry_flag_temp, dma_address_temp[12:3] }
	   			= { 1'b0, dma_address[12:3] } + 1;
	  end
	  else begin
	    if ( addr_carry_flag == 1 ) begin
	      dma_address_temp[DRAM_ADDRESS_SIZE-1:13]
			= dma_address[DRAM_ADDRESS_SIZE-1:13] + 1;
	      addr_carry_flag_temp	= 0;
	    end
	    // flush length functionality
	    if ( bit_rate_reg == 0 ) begin
	      length_reg_temp		= 0;
	    end
	  end
	end						// length_reg != 0
  end // combinatorial logic

  // length state machine registers
  always @( posedge clk) begin
    if ( reset_l == 0 ) begin
      length_reg		<= 0;
      length2_loaded_flag	<= 0;
      interrupt_flag		<= 0;
      addr_carry_flag		<= 0;
      dma_address[13]		<= 0;		// force reset (why?)
      dma_address[3]		<= 0;		// force reset (why?)
    end
    else begin
      length_reg		<= length_reg_temp;
      length2_loaded_flag	<= length2_loaded_flag_temp;
      interrupt_flag		<= interrupt_flag_temp;
      addr_carry_flag		<= addr_carry_flag_temp;
      dma_address 		<= dma_address_temp;
    end
  end

  // sound data fifo state machine

  always @( posedge clk) begin
     if ( reset_l == 0 ) begin
	word_select		<= 0;
	data_available_flag	<= 0;
	dfifo2_loaded_flag	<= 0;
	current_sample		<= 0;	// reset to avoid pop
	// dont care's during reset
     end
     else begin
       if ( data_available_flag == 0 ) begin
	 if ( dfifo2_loaded_flag == 1 ) begin
	   				// load data from next to current
	   data_available_flag	<= 1;
	   audio_data		<= next_data;
	   word_select		<= 1;
	   dfifo2_loaded_flag	<= 0;
	 end
       end
       else begin 	// ( data_available_flag == 1 )
	 if ( abus_word3 == 0 && abus_word2 == 1 ) begin  // rising edge
	   if ( word_select == 1 ) begin
             current_sample <= audio_data[63:32];	// high word 1st
	     word_select		<= 0;
	   end
	   else begin
             current_sample <= audio_data[31:0];	// low word 2nd
	     data_available_flag	<= 0;
	   end
	   // $display("ai_current sample %8h", audio_data);
	 end
       end
       if ( dfifo2_loaded_flag == 0 ) begin
         if ( state == STATE_READ && dma_start ) begin	// got DMA data 
	   				// load next data line 
	   dfifo2_loaded_flag	<= 1;
           next_data		<= dbus_data;
	   // $display("ai_next sample %8h", dbus_data);
	 end
       end

     end
  end

  // dma_request state machine

  always @( posedge clk) begin
    if ( reset_l == 0 ) begin
       state		<= STATE_IDLE;
       dma_busy		<= LOW;
       dma_request	<= LOW;
    end
    else begin
       case (state)
           STATE_IDLE : begin
	       if ( dma_request == LOW && dma_busy == LOW ) begin
		 if ( dma_enable == 1 &&
		      !length_zero && dfifo2_loaded_flag == 0 ) begin
		   dma_busy	<= HIGH;
		   dma_request	<= HIGH;
		 end
	       end
               if ( dma_request == HIGH && dma_grant ) begin		
	         dma_request	<= LOW; 	// DMA operation has begun
                 state		<= STATE_READ;
               end
               else begin
                 state		<= STATE_IDLE;
               end
             end

           STATE_READ : begin
	       if ( dma_start ) begin
	         if ( dma_busy == HIGH ) begin
	           dma_busy	<= LOW; 	// got DMA data 
		 end
                 state		<= STATE_IDLE;
	       end
               else begin
                 state		<= STATE_READ;
               end
             end
	   // state decode is complete
        endcase
     end
  end

  // register write logic

  always @( posedge clk) begin
     if (reset_l == 0) begin
	bit_rate_reg	<= 0;		// reset for testability
        dma_enable	<= 0;
	dac_rate_reg	<= 0;           // reset for testability
     end
     else begin
        if ( reg_write_enable ) begin
	   case (reg_address) // 
              AI_DRAM_ADDRESS_REG : begin
                  next_dma_address	<= { reg_write_data[31:3], 3'b0 };
                end

              AI_LENGTH_REG : begin
                  next_dma_length <= reg_write_data[LENGTH_COUNT_SIZE-1:3];

                  // if (length2_loaded_flag) begin
                    // $display("Panic!  AI DMA request overflow.");
                  // end
                end

              AI_DACRATE_REG : begin
		  dac_rate_reg <= reg_write_data[DAC_RATE_SIZE-1:0];
	          // $display("ai_dac_rate %8h", reg_write_data);
                end

              AI_BITRATE_REG : begin
		  bit_rate_reg <= reg_write_data[3:0];
	          // $display("ai_bit_rate %8h", reg_write_data);
                end

	      AI_CONTROL_REG : begin
		  dma_enable   <= reg_write_data[0];
                end

              default : begin
                 // $display("Panic!  Illegal AI register write - <%h>.",
                   // reg_address);
                 // $finish;
                end
           endcase
         end  // reg_write_enable
     end  // not reset
  end  // always

  //  status register
  always @( length2_loaded_flag or length_zero or
	    dma_busy or dma_request or dma_enable or
	    dfifo2_loaded_flag or data_available_flag or word_select or
	    abus_word2 or test_data ) begin

    status_data = { length2_loaded_flag, !length_zero, 2'b0,
		    dma_busy, dma_request, dma_enable, 1'b1,
		dfifo2_loaded_flag, data_available_flag, word_select, 1'b1,
		    abus_word2, 2'b0, test_data[0],
		    test_data[15:1] ,length2_loaded_flag};
    // $display("ai_status reg read %h", status_data);
  end

  // register read mux
  always @( reg_address or length_reg or status_data ) begin

     case (reg_address)
	// AI_DRAM_ADDRESS_REG : reg_read_data = dma_address;
	AI_LENGTH_REG : reg_read_data = { 11'b0, length_reg, 3'b0 };
	AI_STATUS_REG : reg_read_data = status_data;
	default :       reg_read_data = { 11'b0, length_reg, 3'b0 };
					// for complete decode
    endcase
  end

endmodule
// eof