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------------------------------------------------------------------------------- -- -- The Opcode Decoder. -- Derives instruction mnemonics and multicycle information -- using the OPC table unit. -- -- $Id: opc_decoder.vhd,v 1.3 2005-06-11 10:08:43 arniml Exp $ -- -- Copyright (c) 2004, Arnim Laeuger (arniml@opencores.org) -- -- All rights reserved -- -- Redistribution and use in source and synthezised 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 synthesized 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 author nor the names of other 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 AUTHOR 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. -- -- Please report bugs to the author, but before you do so, please -- make sure that this is not a derivative work and that -- you have the latest version of this file. -- -- The latest version of this file can be found at: -- http://www.opencores.org/cvsweb.shtml/t48/ -- ------------------------------------------------------------------------------- library ieee; use ieee.std_logic_1164.all; use work.t48_pack.word_t; use work.t48_decoder_pack.mnemonic_t; entity t48_opc_decoder is generic ( -- store mnemonic in flip-flops (registered-out) register_mnemonic_g : integer := 1 ); port ( -- Global Interface ------------------------------------------------------- clk_i : in std_logic; res_i : in std_logic; en_clk_i : in boolean; -- T48 Bus Interface ------------------------------------------------------ data_i : in word_t; read_bus_i : in boolean; -- Decoder Interface ------------------------------------------------------ inj_int_i : in boolean; opcode_o : out word_t; mnemonic_o : out mnemonic_t; multi_cycle_o : out boolean ); end t48_opc_decoder; use work.t48_pack.clk_active_c; use work.t48_pack.res_active_c; use work.t48_pack.to_boolean; --use work.decoder_pack.MN_NOP; use work.t48_decoder_pack.all; use work.t48_comp_pack.t48_opc_table; architecture rtl of t48_opc_decoder is -- the opcode register signal opcode_q : word_t; -- the mnemonic signal mnemonic_s, mnemonic_q : mnemonic_t; signal multi_cycle_s : std_logic; begin ----------------------------------------------------------------------------- -- Verify the generics ----------------------------------------------------------------------------- -- pragma translate_off -- Register Mnemonic -------------------------------------------------------- assert (register_mnemonic_g = 1) or (register_mnemonic_g = 0) report "register_mnemonic_g must be either 1 or 0!" severity failure; -- pragma translate_on ----------------------------------------------------------------------------- -- Opcode Decoder Table ----------------------------------------------------------------------------- opc_table_b : t48_opc_table port map ( opcode_i => opcode_q, multi_cycle_o => multi_cycle_s, mnemonic_o => mnemonic_s ); ----------------------------------------------------------------------------- -- Process regs -- -- Purpose: -- Implements the opcode and mnemonic registers. -- regs: process (res_i, clk_i) begin if res_i = res_active_c then opcode_q <= (others => '0'); -- NOP mnemonic_q <= MN_NOP; elsif clk_i'event and clk_i = clk_active_c then if en_clk_i then if read_bus_i then opcode_q <= data_i; elsif inj_int_i then opcode_q <= "00010100"; else mnemonic_q <= mnemonic_s; end if; end if; end if; end process regs; -- ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- -- Output Mapping. ----------------------------------------------------------------------------- opcode_o <= opcode_q; multi_cycle_o <= to_boolean(multi_cycle_s); mnemonic_o <= mnemonic_q when register_mnemonic_g = 1 else mnemonic_s; end rtl; ------------------------------------------------------------------------------- -- File History: -- -- $Log: not supported by cvs2svn $ -- Revision 1.2 2004/07/11 16:51:33 arniml -- cleanup copyright notice -- -- Revision 1.1 2004/03/23 21:31:52 arniml -- initial check-in -- -------------------------------------------------------------------------------