//======================================================================
//
// fw_ram.v
// --------
// A 1024 x 32 bit RAM (4096 bytes) for use by the FW. The memory has
// support for mode based access control.
//
// Author: Joachim Strombergson
// Copyright (C) 2022 - Tillitis AB
// SPDX-License-Identifier: GPL-2.0-only
//
//======================================================================

`default_nettype none

module fw_ram(
	      input  wire          clk,
	      input  wire          reset_n,

	      input  wire          fw_app_mode,

              input  wire          cs,
	      input  wire [3 : 0]  we,
	      input  wire [9 : 0]  address,
	      input  wire [31 : 0] write_data,
	      output wire [31 : 0] read_data,
	      output wire          ready
             );


  //----------------------------------------------------------------
  // Registers and wires.
  //----------------------------------------------------------------
  reg [31 : 0] tmp_read_data;
  reg [31 : 0] mem_read_data0;
  reg [31 : 0] mem_read_data1;
  reg [31 : 0] mem_read_data2;
  reg [31 : 0] mem_read_data3;
  reg          ready_reg;
  wire         fw_app_cs;
  reg          bank0;
  reg          bank1;
  reg          bank2;
  reg          bank3;


  //----------------------------------------------------------------
  // Concurrent assignment of ports.
  //----------------------------------------------------------------
  assign read_data = tmp_read_data;
  assign ready     = ready_reg;
  assign fw_app_cs = cs && ~fw_app_mode;


  //----------------------------------------------------------------
  // Block RAM instances.
  //----------------------------------------------------------------
  // Bank0
  SB_RAM40_4K fw_ram0_0(
			.RDATA(mem_read_data0[15 : 0]),
			.RADDR({3'h0, address[7 : 0]}),
			.RCLK(clk),
			.RCLKE(1'h1),
			.RE(fw_app_cs & bank0),
			.WADDR({3'h0, address[7 : 0]}),
			.WCLK(clk),
			.WCLKE(1'h1),
			.WDATA(write_data[15 : 0]),
			.WE((|we & fw_app_cs & bank0)),
			.MASK({{8{~we[1]}}, {8{~we[0]}}})
			);

  SB_RAM40_4K fw_ram0_1(
			.RDATA(mem_read_data0[31 : 16]),
			.RADDR({3'h0, address[7 : 0]}),
			.RCLK(clk),
			.RCLKE(1'h1),
			.RE(fw_app_cs & bank0),
			.WADDR({3'h0, address[7 : 0]}),
			.WCLK(clk),
			.WCLKE(1'h1),
			.WDATA(write_data[31 : 16]),
			.WE((|we & fw_app_cs & bank0)),
			.MASK({{8{~we[3]}}, {8{~we[2]}}})
			);

  // Bank1
  SB_RAM40_4K fw_ram1_0(
			.RDATA(mem_read_data1[15 : 0]),
			.RADDR({3'h0, address[7 : 0]}),
			.RCLK(clk),
			.RCLKE(1'h1),
			.RE(fw_app_cs & bank1),
			.WADDR({3'h0, address[7 : 0]}),
			.WCLK(clk),
			.WCLKE(1'h1),
			.WDATA(write_data[15 : 0]),
			.WE((|we & fw_app_cs & bank1)),
			.MASK({{8{~we[1]}}, {8{~we[0]}}})
		       );

  SB_RAM40_4K fw_ram1_1(
			.RDATA(mem_read_data1[31 : 16]),
			.RADDR({3'h0, address[7 : 0]}),
			.RCLK(clk),
			.RCLKE(1'h1),
			.RE(fw_app_cs & bank1),
			.WADDR({3'h0, address[7 : 0]}),
			.WCLK(clk),
			.WCLKE(1'h1),
			.WDATA(write_data[31 : 16]),
			.WE((|we & fw_app_cs & bank1)),
			.MASK({{8{~we[3]}}, {8{~we[2]}}})
			);

  // Bank2
  SB_RAM40_4K fw_ram2_0(
			.RDATA(mem_read_data2[15 : 0]),
			.RADDR({3'h0, address[7 : 0]}),
			.RCLK(clk),
			.RCLKE(1'h1),
			.RE(fw_app_cs & bank2),
			.WADDR({3'h0, address[7 : 0]}),
			.WCLK(clk),
			.WCLKE(1'h1),
			.WDATA(write_data[15 : 0]),
			.WE((|we & fw_app_cs & bank2)),
			.MASK({{8{~we[1]}}, {8{~we[0]}}})
			);

  SB_RAM40_4K fw_ram2_1(
			.RDATA(mem_read_data2[31 : 16]),
			.RADDR({3'h0, address[7 : 0]}),
			.RCLK(clk),
			.RCLKE(1'h1),
			.RE(fw_app_cs & bank2),
			.WADDR({3'h0, address[7 : 0]}),
			.WCLK(clk),
			.WCLKE(1'h1),
			.WDATA(write_data[31 : 16]),
			.WE((|we & fw_app_cs & bank2)),
			.MASK({{8{~we[3]}}, {8{~we[2]}}})
			);

  // Bank3
  SB_RAM40_4K fw_ram3_0(
			.RDATA(mem_read_data3[15 : 0]),
			.RADDR({3'h0, address[7 : 0]}),
			.RCLK(clk),
			.RCLKE(1'h1),
			.RE(fw_app_cs & bank3),
			.WADDR({3'h0, address[7 : 0]}),
			.WCLK(clk),
			.WCLKE(1'h1),
			.WDATA(write_data[15 : 0]),
			.WE((|we & fw_app_cs & bank3)),
			.MASK({{8{~we[1]}}, {8{~we[0]}}})
			);

  SB_RAM40_4K fw_ram3_1(
			.RDATA(mem_read_data3[31 : 16]),
			.RADDR({3'h0, address[7 : 0]}),
			.RCLK(clk),
			.RCLKE(1'h1),
			.RE(fw_app_cs & bank3),
			.WADDR({3'h0, address[7 : 0]}),
			.WCLK(clk),
			.WCLKE(1'h1),
			.WDATA(write_data[31 : 16]),
			.WE((|we & fw_app_cs & bank3)),
			.MASK({{8{~we[3]}}, {8{~we[2]}}})
			);

  //----------------------------------------------------------------
  // reg_update
  //----------------------------------------------------------------
  always @(posedge clk)
    begin : reg_update
      if (!reset_n) begin
        ready_reg <= 1'h0;
      end
      else begin
        ready_reg <= cs;
      end
    end


  //----------------------------------------------------------------
  // rw_mux
  //----------------------------------------------------------------
  always @*
    begin : rw_mux;
      bank0         = 1'h0;
      bank1         = 1'h0;
      bank2         = 1'h0;
      bank3         = 1'h0;

      if (fw_app_cs) begin
	case(address[9 : 8])
	  0: begin
	    bank0 = 1'h1;
	    tmp_read_data = mem_read_data0;
	  end

	  1: begin
	    bank1 = 1'h1;
	    tmp_read_data = mem_read_data1;
	  end

	  2: begin
	    bank2 = 1'h1;
	    tmp_read_data = mem_read_data2;
	  end

	  3: begin
	    bank3 = 1'h1;
	    tmp_read_data = mem_read_data3;
	  end

	  default: begin
	  end
	endcase // case (address[9 : 8])
      end
    end

endmodule // fw_ram

//======================================================================
// EOF fw_ram.v
//======================================================================