Subversion Repositories tinyvliw8

-------------------------------------------------------------------------------
--
-- Design:  tinyVLIW8 soft-core processor
-- Author:  Oliver Stecklina <stecklina@ihp-microelectronics.com>
-- Date:    03.02.2014 
-- File:    instDecoder.vhd
--
-------------------------------------------------------------------------------
--
-- Description : This unit is the instruction set decoder of the
--               embedded 8-bit VLIW processor.
--
-------------------------------------------------------------------------------
--
--    Copyright (C) 2015 IHP GmbH, Frankfurt (Oder), Germany
--
-- This code is free software. It is licensed under the EUPL, Version 1.1
-- or - as soon they will be approved by the European Commission - subsequent
-- versions of the EUPL (the "License").
-- You may redistribute this code and/or modify it under the terms of this
-- License.
-- You may not use this work except in compliance with the License.
-- You may obtain a copy of the License at:
--
-- http://joinup.ec.europa.eu/software/page/eupl/licence-eupl
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" basis,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.
--
-------------------------------------------------------------------------------
 
library ieee;
 
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
 
entity vliwProc_instDecoder is
	port (
		clk        : in std_logic;
 
		instData   : in  std_logic_vector(31 downto 0);
 
		ldstOpCode : out std_logic;
		ldstAs     : out std_logic_vector(1 downto 0);
		ldstDstReg : out std_logic_vector(2 downto 0);
		ldstSrc    : out std_logic_vector(7 downto 0);
		ldstEn_n   : out std_logic;
 
		aluOpCode  : out std_logic_vector(2 downto 0);
		aluAs      : out std_logic_vector(1 downto 0);
		aluDstReg  : out std_logic_vector(2 downto 0);
		aluSrc     : out std_logic_vector(7 downto 0);
		aluEn_n    : out std_logic;
 
		jmpAs      : out std_logic_vector(1 downto 0);
		jmpDstReg  : out std_logic_vector(10 downto 0);
		jmpEn_n    : out std_logic;
 
		esb        : out std_logic_vector(3 downto 0);
 
		stalled_n  : out std_logic;	
		stall_n    : in std_logic;	
 
		rst_n      : in std_logic
	);
end vliwProc_instDecoder;
 
architecture behavior of vliwProc_instDecoder is
 
component gendelay
	generic (n: integer := 1);
	port (
		a_in	: in	std_logic;
		a_out	: out	std_logic
	);
end component;
 
	signal instWord0_s  : std_logic_vector(15 downto 0);
	signal instWord1_s  : std_logic_vector(15 downto 0);
 
	signal clk_s          : std_logic;
 
	signal esb_s           : std_logic_vector(3 downto 0);
 
	signal untSel0_n_s : std_logic_vector(2 downto 0);
	signal untSel1_n_s : std_logic_vector(2 downto 0);
 
	signal stalled_n_s : std_logic;
 
	signal ldstEn_n_s  : std_logic;
	signal aluEn_n_s   : std_logic;
	signal jmpEn_n_s   : std_logic;
 
	signal cnt_s      : std_logic_vector(1 downto 0);	
begin
 
	clk_s     <= clk;
	stalled_n <= stalled_n_s;
 
	-- Note! use cnt_s instead of esb to be faster than esb
	--    otherwise we get a glitch on esb(0) in case of stall
	sync_Stall: process(rst_n, cnt_s(0))
	begin
		if (rst_n = '0') then
			stalled_n_s <= '1';
		else
			if (cnt_s(0)'event and cnt_s(0) = '1') then
				stalled_n_s <= stall_n;
			end if;
		end if;
	end process;
 
	ldstEn_n <= ldstEn_n_s;
	jmpEn_n <= jmpEn_n_s;
	aluEn_n <= aluEn_n_s;
 
	genState_p : process(rst_n, clk_s)
	begin
		if (rst_n = '0') then
			cnt_s <= "01";
		else
			if (clk_s'event and clk_s = '0') then
				cnt_s(1) <= not(cnt_s(1));
			end if;
 
			if (clk_s'event and clk_s = '1') then
				cnt_s(0) <= not(cnt_s(0));
			end if;
		end if;
	end process;
 
	-- execution state bus
	esb_s <= "0001" when rst_n = '1' and cnt_s = "01" else
	         "0010" when rst_n = '1' and cnt_s = "11" else
	         "0100" when rst_n = '1' and cnt_s = "10" else
	         "1000" when rst_n = '1' and cnt_s = "00" else
	         "0000";
 
	esb <= esb_s when stalled_n_s = '1' else
	       (others => '0');
 
	untSel1_n_s <= "111" when instWord0_s(15 downto 13) = instWord1_s(15 downto 13) else
	               "110" when instWord1_s(15 downto 13) = "111" else
				   "101" when instWord1_s(15 downto 13) = "000" or instWord1_s(15 downto 13) = "001" else
				   "011";
 
	untSel0_n_s <= "110" when instWord0_s(15 downto 13) = "111" else
				   "101" when instWord0_s(15 downto 13) = "000" or instWord0_s(15 downto 13) = "001" else
				   "011";
 
 
	jmpEn_n_s  <= '0' when (untSel0_n_s(0) = '0' or untSel1_n_s(0) = '0') and cnt_s(1) = '1' else
	              '1';
	ldstEn_n_s <= '0' when (untSel0_n_s(1) = '0' or untSel1_n_s(1) = '0') and cnt_s(1) = '1' else
	              '1';
	aluEn_n_s  <= '0' when (untSel0_n_s(2) = '0' or untSel1_n_s(2) = '0') and cnt_s(1) = '1' else
	              '1';
 
	instWord0_s <= instData(31 downto 16);
	instWord1_s <= instData(15 downto 0);
 
	aluOpCode  <= instWord0_s(15 downto 13)  when untSel0_n_s(2) = '0' else
	              instWord1_s(15 downto 13)  when untSel1_n_s(2) = '0' else
	              (others => '0');
	aluAs      <= instWord0_s(12 downto 11) when untSel0_n_s(2) = '0' else
	              instWord1_s(12 downto 11) when untSel1_n_s(2) = '0' else
	              (others => '0');
	aluDstReg  <= instWord0_s(10 downto 8)  when untSel0_n_s(2) = '0' else
	              instWord1_s(10 downto 8)  when untSel1_n_s(2) = '0' else
	              (others => '0');
	aluSrc     <= instWord0_s(7 downto 0)   when untSel0_n_s(2) = '0' else
	              instWord1_s(7 downto 0)   when untSel1_n_s(2) = '0' else
	              (others => '0');
 
	ldstOpCode  <= instWord0_s(13)           when untSel0_n_s(1) = '0' else
	               instWord1_s(13)           when untSel1_n_s(1) = '0' else
	               '0';
	ldstAs      <= instWord0_s(12 downto 11) when untSel0_n_s(1) = '0' else
	               instWord1_s(12 downto 11) when untSel1_n_s(1) = '0' else
	               (others => '0');
	ldstDstReg  <= instWord0_s(10 downto 8)  when untSel0_n_s(1) = '0' else
	               instWord1_s(10 downto 8)  when untSel1_n_s(1) = '0' else
	               (others => '0');
	ldstSrc     <= instWord0_s(7 downto 0)   when untSel0_n_s(1) = '0' else
	               instWord1_s(7 downto 0)   when untSel1_n_s(1) = '0' else
	               (others => '0');
 
	jmpAs      <= instWord0_s(12 downto 11) when untSel0_n_s(0) = '0' else
	              instWord1_s(12 downto 11) when untSel1_n_s(0) = '0' else
	              (others => '0');
	jmpDstReg  <= instWord0_s(10 downto 0)  when untSel0_n_s(0) = '0' else
	              instWord1_s(10 downto 0)  when untSel1_n_s(0) = '0' else
	              (others => '0');
 
end behavior;