-- ***************************************************************************
-- ***************************************************************************
-- Copyright 2014 - 2017 (c) Analog Devices, Inc. All rights reserved.
--
-- In this HDL repository, there are many different and unique modules, consisting
-- of various HDL (Verilog or VHDL) components. The individual modules are
-- developed independently, and may be accompanied by separate and unique license
-- terms.
--
-- The user should read each of these license terms, and understand the
-- freedoms and responsabilities that he or she has by using this source/core.
--
-- This core 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.
--
-- Redistribution and use of source or resulting binaries, with or without modification
-- of this file, are permitted under one of the following two license terms:
--
--   1. The GNU General Public License version 2 as published by the
--      Free Software Foundation, which can be found in the top level directory
--      of this repository (LICENSE_GPL2), and also online at:
--      <https://www.gnu.org/licenses/old-licenses/gpl-2.0.html>
--
-- OR
--
--   2. An ADI specific BSD license, which can be found in the top level directory
--      of this repository (LICENSE_ADIBSD), and also on-line at:
--      https://github.com/analogdevicesinc/hdl/blob/master/LICENSE_ADIBSD
--      This will allow to generate bit files and not release the source code,
--      as long as it attaches to an ADI device.
--
-- ***************************************************************************
-- ***************************************************************************

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity axi_ctrlif is
	generic
	(
		C_NUM_REG			: integer			:= 32;
		C_S_AXI_DATA_WIDTH	: integer			:= 32;
		C_S_AXI_ADDR_WIDTH	: integer			:= 32;
		C_FAMILY		: string			:= "virtex6"
	);
	port
	(
		-- AXI bus interface
		s_axi_aclk		: in  std_logic;
		s_axi_aresetn		: in  std_logic;
		s_axi_awaddr		: in  std_logic_vector(C_S_AXI_ADDR_WIDTH-1 downto 0);
		s_axi_awvalid		: in  std_logic;
		s_axi_wdata		: in  std_logic_vector(C_S_AXI_DATA_WIDTH-1 downto 0);
		s_axi_wstrb		: in  std_logic_vector((C_S_AXI_DATA_WIDTH/8)-1 downto 0);
		s_axi_wvalid		: in  std_logic;
		s_axi_bready		: in  std_logic;
		s_axi_araddr		: in  std_logic_vector(C_S_AXI_ADDR_WIDTH-1 downto 0);
		s_axi_arvalid		: in  std_logic;
		s_axi_rready		: in  std_logic;
		s_axi_arready		: out std_logic;
		s_axi_rdata		: out std_logic_vector(C_S_AXI_DATA_WIDTH-1 downto 0);
		s_axi_rresp		: out std_logic_vector(1 downto 0);
		s_axi_rvalid		: out std_logic;
		s_axi_wready		: out std_logic;
		s_axi_bresp		: out std_logic_vector(1 downto 0);
		s_axi_bvalid		: out std_logic;
		s_axi_awready		: out std_logic;

		rd_addr : out integer range 0 to C_NUM_REG - 1;
		rd_data : in  std_logic_vector(C_S_AXI_DATA_WIDTH-1 downto 0);
		rd_ack  : out std_logic;
		rd_stb  : in  std_logic;

		wr_addr : out integer range 0 to C_NUM_REG - 1;
		wr_data : out std_logic_vector(C_S_AXI_DATA_WIDTH-1 downto 0);
		wr_ack  : in  std_logic;
		wr_stb  : out std_logic
	);
end entity axi_ctrlif;


architecture Behavioral of axi_ctrlif is
	type state_type is (IDLE, RESP, ACK);
	signal rd_state : state_type;
	signal wr_state : state_type;
begin
	process (s_axi_aclk)
	begin
		if rising_edge(s_axi_aclk) then
			if s_axi_aresetn = '0' then
				rd_state <= IDLE;
			else
				case rd_state is
				when IDLE =>
					if s_axi_arvalid = '1' then
						rd_state <= RESP;
						rd_addr <= to_integer(unsigned(s_axi_araddr((C_S_AXI_ADDR_WIDTH-1) downto 2)));
					end if;
				when RESP =>
					if rd_stb = '1' and s_axi_rready = '1' then
						rd_state <= IDLE;
					end if;
				when others => null;
				end case;
			end if;
		end if;
	end process;

	s_axi_arready <= '1' when rd_state = IDLE else '0';
	s_axi_rvalid <= '1' when rd_state = RESP and rd_stb = '1' else '0';
	s_axi_rresp <= "00";
	rd_ack <= '1' when rd_state = RESP and s_axi_rready = '1' else '0';
	s_axi_rdata <= rd_data;

	process (s_axi_aclk)
	begin
		if rising_edge(s_axi_aclk) then
			if s_axi_aresetn = '0' then
				wr_state <= IDLE;
			else
				case wr_state is
				when IDLE =>
					if s_axi_awvalid = '1' and s_axi_wvalid = '1' and wr_ack = '1' then
						wr_state <= ACK;
					end if;
				when ACK =>
					wr_state <= RESP;
				when RESP =>
					if s_axi_bready = '1' then
						wr_state <= IDLE;
					end if;
				end case;
			end if;
		end if;
	end process;

	wr_stb <= '1' when s_axi_awvalid = '1' and s_axi_wvalid = '1' and wr_state = IDLE else '0';
	wr_data <= s_axi_wdata;
	wr_addr <= to_integer(unsigned(s_axi_awaddr((C_S_AXI_ADDR_WIDTH-1) downto 2)));

	s_axi_awready <= '1' when wr_state = ACK else '0';
	s_axi_wready <= '1' when wr_state = ACK else '0';

	s_axi_bresp <= "00";
	s_axi_bvalid <= '1' when wr_state = RESP else '0';
end;