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[/] [w11/] [tags/] [w11a_V0.5/] [rtl/] [w11a/] [pdp11_lbox.vhd] - Blame information for rev 7

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1 2 wfjm 
-- $Id: pdp11_lbox.vhd 314 2010-07-09 17:38:41Z mueller $
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--
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-- Copyright 2006-2008 by Walter F.J. Mueller <W.F.J.Mueller@gsi.de>
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--
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-- This program is free software; you may redistribute and/or modify it under
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-- the terms of the GNU General Public License as published by the Free
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-- Software Foundation, either version 2, or at your option any later version.
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--
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-- This program is distributed in the hope that it will be useful, but
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-- WITHOUT ANY WARRANTY, without even the implied warranty of MERCHANTABILITY
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-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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-- for complete details.
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--
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------------------------------------------------------------------------------
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-- Module Name:    pdp11_lbox - syn
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-- Description:    pdp11: logic unit for data (lbox)
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--
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-- Dependencies:   -
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-- Test bench:     tb/tb_pdp11_core (implicit)
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-- Target Devices: generic
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-- Tool versions:  xst 8.1, 8.2, 9.1, 9.2; ghdl 0.18-0.25
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-- Revision History:
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-- Date         Rev Version  Comment
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-- 2008-03-30   131   1.0.2  BUGFIX: SXT clears V condition code
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-- 2007-06-14    56   1.0.1  Use slvtypes.all
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-- 2007-05-12    26   1.0    Initial version
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------------------------------------------------------------------------------
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library ieee;
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use ieee.std_logic_1164.all;
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use ieee.std_logic_arith.all;
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use work.slvtypes.all;
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use work.pdp11.all;
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-- ----------------------------------------------------------------------------
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entity pdp11_lbox is                    -- logic unit for data (lbox)
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  port (
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    DSRC : in slv16;                    -- 'src' data in
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    DDST : in slv16;                    -- 'dst' data in
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    CCIN : in slv4;                     -- condition codes in
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    FUNC : in slv4;                     -- function
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    BYTOP : in slbit;                   -- byte operation
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    DOUT : out slv16;                   -- data output
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    CCOUT : out slv4                    -- condition codes out
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  );
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end pdp11_lbox;
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architecture syn of pdp11_lbox is
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-- --------------------------------------
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begin
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  process (DSRC, DDST, CCIN, FUNC, BYTOP)
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    variable iout : slv16 := (others=>'0');
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    variable inzstd : slbit := '0';
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    variable ino : slbit := '0';
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    variable izo : slbit := '0';
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    variable ivo : slbit := '0';
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    variable ico : slbit := '0';
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    alias DSRC_L : slv8 is DSRC(7 downto 0);
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    alias DSRC_H : slv8 is DSRC(15 downto 8);
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    alias DDST_L : slv8 is DDST(7 downto 0);
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    alias DDST_H : slv8 is DDST(15 downto 8);
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    alias NI : slbit is CCIN(3);
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    alias ZI : slbit is CCIN(2);
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    alias VI : slbit is CCIN(1);
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    alias CI : slbit is CCIN(0);
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    alias iout_l : slv8 is iout(7 downto 0);
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    alias iout_h : slv8 is iout(15 downto 8);
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  begin
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    iout := (others=>'0');
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    inzstd := '1';                      -- use standard logic by default
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    ino := '0';
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    izo := '0';
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    ivo := '0';
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    ico := '0';
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--
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-- the decoding of FUNC is done "manually" to get a structure based on
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-- a 8->1 pattern. This matches the opcode structure and seems most
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-- efficient.
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--
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    if FUNC(3) = '0' then
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      if BYTOP = '0' then
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        case FUNC(2 downto 0) is
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          when "000" =>                 -- ASR
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            iout := DDST(15) & DDST(15 downto 1);
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            ico := DDST(0);
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            ivo := iout(15) xor ico;
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          when "001"  =>                -- ASL
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            iout := DDST(14 downto 0) & '0';
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            ico := DDST(15);
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            ivo := iout(15) xor ico;
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          when "010" =>                 -- ROR
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            iout := CI & DDST(15 downto 1);
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            ico := DDST(0);
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            ivo := iout(15) xor ico;
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          when "011"  =>                -- ROL
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            iout := DDST(14 downto 0) & CI;
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            ico := DDST(15);
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            ivo := iout(15) xor ico;
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          when "100" =>                 -- BIS
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            iout := DDST or DSRC;
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            ico := CI;
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          when "101" =>                 -- BIC
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            iout := DDST and not DSRC;
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            ico := CI;
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          when "110" =>                 -- BIT
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            iout := DDST and DSRC;
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            ico := CI;
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          when "111" =>                 -- MOV
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            iout := DSRC;
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            ico := CI;
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          when others => null;
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        end case;
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      else
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        case FUNC(2 downto 0) is
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          when "000" =>                 -- ASRB
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            iout_l := DDST_L(7) & DDST_L(7 downto 1);
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            ico := DDST_L(0);
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            ivo := iout_l(7) xor ico;
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          when "001"  =>                -- ASLB
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            iout_l := DDST(6 downto 0) & '0';
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            ico := DDST(7);
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            ivo := iout_l(7) xor ico;
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          when "010" =>                 -- RORB
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            iout_l := CI & DDST_L(7 downto 1);
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            ico := DDST_L(0);
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            ivo := iout_l(7) xor ico;
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          when "011"  =>                -- ROLB
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            iout_l := DDST_L(6 downto 0) & CI;
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            ico := DDST_L(7);
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            ivo := iout_l(7) xor ico;
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          when "100" =>                 -- BISB
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            iout_l := DDST_L or DSRC_L;
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            ico := CI;
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          when "101" =>                 -- BICB
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            iout_l := DDST_L and not DSRC_L;
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            ico := CI;
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          when "110" =>                 -- BITB
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            iout_l := DDST_L and DSRC_L;
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            ico := CI;
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          when "111" =>                 -- MOVB
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            iout_l := DSRC_L;
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            iout_h := (others=>DSRC_L(7));
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            ico := CI;
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          when others => null;
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        end case;
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      end if;
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    else
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      case FUNC(2 downto 0) is
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        when "000" =>                   -- SXT
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          iout := (others=>NI);
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          inzstd := '0';
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          ino := NI;
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          izo := not NI;
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          ivo := '0';
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          ico := CI;
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        when "001" =>                   -- SWAP
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          iout := DDST_L & DDST_H;
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          inzstd := '0';
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          ino := iout(7);
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          if unsigned(iout(7 downto 0)) = 0 then
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            izo := '1';
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          else
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            izo := '0';
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          end if;
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        when "010" =>                   -- XOR
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          iout := DDST xor DSRC;
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          ico := CI;
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199 
        when others => null;
200 
 
201 
      end case;
202 
    end if;
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    DOUT <= iout;
205 
 
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    if inzstd = '1' then
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      if BYTOP = '1' then
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        ino := iout(7);
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        if unsigned(iout(7 downto 0)) = 0 then
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          izo := '1';
211 
        else
212 
          izo := '0';
213 
        end if;
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      else
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        ino := iout(15);
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        if unsigned(iout) = 0 then
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          izo := '1';
218 
        else
219 
          izo := '0';
220 
        end if;
221 
      end if;
222 
    end if;
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224 
    CCOUT(3) <= ino;
225 
    CCOUT(2) <= izo;
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    CCOUT(1) <= ivo;
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    CCOUT(0) <= ico;
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  end process;
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end syn;

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