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[/] [cpu_lecture/] [trunk/] [src/] [status_reg.vhd] - Rev 14
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------------------------------------------------------------------------------- -- -- Copyright (C) 2009, 2010 Dr. Juergen Sauermann -- -- This code is free software: you can redistribute it and/or modify -- it under the terms of the GNU General Public License as published by -- the Free Software Foundation, either version 3 of the License, or -- (at your option) any later version. -- -- This code 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. See the -- GNU General Public License for more details. -- -- You should have received a copy of the GNU General Public License -- along with this code (see the file named COPYING). -- If not, see http://www.gnu.org/licenses/. -- ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- -- -- Module Name: Register - Behavioral -- Create Date: 16:15:54 12/26/2009 -- Description: the status register of a CPU. -- ---------------------------------------------------------------------------------- library IEEE; use IEEE.STD_LOGIC_1164.ALL; use IEEE.STD_LOGIC_ARITH.ALL; use IEEE.STD_LOGIC_UNSIGNED.ALL; entity status_reg is port ( I_CLK : in std_logic; I_COND : in std_logic_vector ( 3 downto 0); I_DIN : in std_logic_vector ( 7 downto 0); I_FLAGS : in std_logic_vector ( 7 downto 0); I_WE_F : in std_logic; I_WE_SR : in std_logic; Q : out std_logic_vector ( 7 downto 0); Q_CC : out std_logic); end status_reg; architecture Behavioral of status_reg is signal L : std_logic_vector ( 7 downto 0); begin process(I_CLK) begin if (rising_edge(I_CLK)) then if (I_WE_F = '1') then -- write flags (from ALU) L <= I_FLAGS; elsif (I_WE_SR = '1') then -- write I/O L <= I_DIN; end if; end if; end process; cond: process(I_COND, L) begin case I_COND(2 downto 0) is when "000" => Q_CC <= L(0) xor I_COND(3); when "001" => Q_CC <= L(1) xor I_COND(3); when "010" => Q_CC <= L(2) xor I_COND(3); when "011" => Q_CC <= L(3) xor I_COND(3); when "100" => Q_CC <= L(4) xor I_COND(3); when "101" => Q_CC <= L(5) xor I_COND(3); when "110" => Q_CC <= L(6) xor I_COND(3); when others => Q_CC <= L(7) xor I_COND(3); end case; end process; Q <= L; end Behavioral;
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