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[/] [t400/] [tags/] [rel_0_1_beta/] [rtl/] [vhdl/] [t400_skip.vhd] - Rev 132
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------------------------------------------------------------------------------- -- -- The skip unit. -- Skip conditions are checked here and communicated to the decoder unit. -- -- $Id: t400_skip.vhd,v 1.5 2006-06-05 14:20:34 arniml Exp $ -- -- Copyright (c) 2006 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/t400/ -- ------------------------------------------------------------------------------- library ieee; use ieee.std_logic_1164.all; use work.t400_opt_pack.all; use work.t400_pack.all; entity t400_skip is generic ( opt_type_g : integer := t400_opt_type_420_c ); port ( -- System Interface ------------------------------------------------------- ck_i : in std_logic; ck_en_i : in boolean; por_i : in boolean; res_i : in boolean; -- Control Interface ------------------------------------------------------ op_i : in skip_op_t; dec_data_i : in dec_data_t; carry_i : in std_logic; c_i : in std_logic; bd_i : in dw_t; is_lbi_i : in boolean; skip_o : out boolean; skip_lbi_o : out boolean; -- Data Interface --------------------------------------------------------- a_i : in dw_t; m_i : in dw_t; g_i : in dw_t; tim_c_i : in boolean ); end t400_skip; library ieee; use ieee.numeric_std.all; architecture rtl of t400_skip is signal skip_q, skip_next_q : boolean; signal skip_lbi_q : boolean; signal skip_int_q : boolean; begin ----------------------------------------------------------------------------- -- Process skip -- -- Purpose: -- Implements the skip logic. -- skip: process (ck_i, por_i) variable t420_type_v : boolean; begin if por_i then skip_next_q <= false; skip_q <= false; skip_lbi_q <= false; skip_int_q <= false; elsif ck_i'event and ck_i = '1' then if res_i then -- synchronous reset upon external reset event skip_next_q <= false; skip_q <= false; skip_lbi_q <= false; skip_int_q <= false; elsif ck_en_i then t420_type_v := opt_type_g = t400_opt_type_420_c; if ck_en_i then case op_i is -- update skip information ---------------------------------------- when SKIP_UPDATE => skip_q <= skip_next_q; -- also reset skip_next flag skip_next_q <= false; -- reset skip-on-lbi flag when this was not an LBI if not is_lbi_i then skip_lbi_q <= false; end if; -- skip always ---------------------------------------------------- when SKIP_NOW => skip_next_q <= true; -- skip on carry -------------------------------------------------- when SKIP_CARRY => skip_next_q <= carry_i = '1'; -- skip on C ------------------------------------------------------ when SKIP_C => skip_next_q <= c_i = '1'; -- skip on BD underflow ------------------------------------------ when SKIP_BD_UFLOW => skip_next_q <= unsigned(bd_i) = 15; -- skip on BD overflow ------------------------------------------- when SKIP_BD_OFLOW => skip_next_q <= unsigned(bd_i) = 0; -- skip on LBI instruction ---------------------------------------- when SKIP_LBI => skip_lbi_q <= true; -- skip on A and M equal ------------------------------------------ when SKIP_A_M => skip_next_q <= unsigned(a_i) = unsigned(m_i); -- skip on G zero ------------------------------------------------- when SKIP_G_ZERO => skip_next_q <= unsigned(g_i) = 0; -- skip on G bit -------------------------------------------------- when SKIP_G_BIT => skip_next_q <= unsigned(g_i and dec_data_i(dw_range_t)) = 0; -- skip on M bit -------------------------------------------------- when SKIP_M_BIT => skip_next_q <= unsigned(m_i and dec_data_i(dw_range_t)) = 0; -- skip on timer carry -------------------------------------------- when SKIP_TIMER => skip_next_q <= tim_c_i; null; -- push skip state when vectoring to interrupt routine ------------ when SKIP_PUSH => if t420_type_v then -- save next skip flag skip_int_q <= skip_next_q; skip_next_q <= false; -- never skip first instruction of interrupt routine skip_q <= false; end if; -- pop skip state for RET from interrupt routine ------------------ when SKIP_POP => if t420_type_v then -- push'ed info must be pop'ed to skip_next_q as pop'ing -- happens during RET of interrupt routine -- skip info is valid for next instruction skip_next_q <= skip_int_q; skip_int_q <= false; end if; when others => null; end case; end if; end if; end if; end process skip; -- ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- -- Output mapping ----------------------------------------------------------------------------- skip_o <= skip_q; skip_lbi_o <= skip_lbi_q; end rtl; ------------------------------------------------------------------------------- -- File History: -- -- $Log: not supported by cvs2svn $ -- Revision 1.4 2006/05/28 15:35:33 arniml -- fix pop'ing of skip flag -- -- Revision 1.3 2006/05/27 19:16:52 arniml -- interrupt functionality added -- -- Revision 1.2 2006/05/20 02:47:52 arniml -- skip-on-timer implemented -- -- Revision 1.1.1.1 2006/05/06 01:56:45 arniml -- import from local CVS repository, LOC_CVS_0_1 -- -------------------------------------------------------------------------------
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