//======================================================================
//
// core_selector.v
// ---------------
// Core selector Cryptech Novena FPGA framework.
//
//
// Author: Pavel Shatov
// Copyright (c) 2014, NORDUnet A/S All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// - Redistributions of source code must retain the above copyright
//   notice, this list of conditions and the following disclaimer.
//
// - Redistributions in binary form must reproduce the above copyright
//   notice, this list of conditions and the following disclaimer in the
//   documentation and/or other materials provided with the distribution.
//
// - Neither the name of the NORDUnet nor the names of its contributors may
//   be used to endorse or promote products derived from this software
//   without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
// IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
// PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
// TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
//======================================================================

module core_selector
	(
	 input wire           sys_clk,
         input wire           sys_rst,

	 input wire [13: 0]   sys_eim_addr,
         input wire           sys_eim_wr,
         input wire           sys_eim_rd,
         output wire [31 : 0] read_data,
	 input wire [31 : 0]  write_data
	);

		//
		// Internal Registers
		//
	reg	[31: 0]	reg_x					= {32{1'b0}};
	reg	[31: 0]	reg_y					= {32{1'b0}};
	reg	[15: 0]	reg_ctl				= {16{1'b0}};
	reg	[31: 0]	read_data_reg	= {32{1'b0}};


		//
		// Parameters
		//
	localparam	ADDER_BASE_ADDR		= 12'h321;	// upper 12 bits of address
	localparam	ADDER_OFFSET_REG_X	= 2'd0;		// X
	localparam	ADDER_OFFSET_REG_Y	= 2'd1;		// Y
	localparam	ADDER_OFFSET_REG_Z	= 2'd2;		// Z
	localparam	ADDER_OFFSET_REG_SC	= 2'd3;		// {STATUS, CONTROL}


		/* This flag detects whether adder core is being addressed. */
	wire eim_access_adder	= (sys_eim_addr[13:2] == ADDER_BASE_ADDR) ? 1'b1 : 1'b0;

		/* These flags detect whether write or read access is requested. */
	wire eim_access_write	= sys_eim_wr & eim_access_adder;
	wire eim_access_read		= sys_eim_rd & eim_access_adder;


		//
		// Write Request Handler
		//
	always @(posedge sys_clk)
		//
		if (sys_rst) begin
			reg_x					<= {32{1'b0}};
			reg_y					<= {32{1'b0}};
			reg_ctl				<= {16{1'b0}};
		end else if (eim_access_write) begin
			//
			case (sys_eim_addr[1:0])
				ADDER_OFFSET_REG_X:  reg_x <= write_data;
				ADDER_OFFSET_REG_Y:  reg_y <= write_data;
				ADDER_OFFSET_REG_SC: reg_ctl <= write_data[15 : 0];
			endcase
			//
		end


		//
		// Read Request Handler
		//
	wire	[31: 0]	reg_z;
	wire	[15: 0]	reg_sts;

	always @(posedge sys_clk)
		//
		if (sys_rst)					read_data_reg	<= {32{1'b0}};
		//
		else if (eim_access_read) begin
			//
			case (sys_eim_addr[1:0])
				ADDER_OFFSET_REG_X:	read_data_reg	<= reg_x;
				ADDER_OFFSET_REG_Y:	read_data_reg	<= reg_y;
				ADDER_OFFSET_REG_Z:	read_data_reg	<= reg_z;
				ADDER_OFFSET_REG_SC:	read_data_reg	<= {reg_sts, reg_ctl};
			endcase
			//
		end

	assign read_data = read_data_reg;


		//
		// Demo Adder Core
		//
	demo_adder adder_core
	(
		.clk	(sys_clk),
		.rst	(sys_rst),

		.x		(reg_x),
		.y		(reg_y),
		.z		(reg_z),

		.ctl	(reg_ctl),
		.sts	(reg_sts)
	);



endmodule

//======================================================================
// EOF core_selector.v
//======================================================================