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wfjm.w11/rtl/w11a/pdp11_decode.vhd
Walter F.J. Mueller 3f455d5236 - interim release w11a_V0.532 (untagged) 
- re-organize modules 'human I/O' interface on Digilent boards
- add test designs for 'human I/O' interface for atlys,nexys2, and s3board
- small updates in crc8 and dcm areas
- with one exception all vhdl sources use now numeric_std
2011-11-20 12:31:43 +00:00

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-- $Id: pdp11_decode.vhd 427 2011-11-19 21:04:11Z mueller $
--
-- Copyright 2006-2011 by Walter F.J. Mueller <W.F.J.Mueller@gsi.de>
--
-- This program is free software; you may redistribute and/or modify it under
-- the terms of the GNU General Public License as published by the Free
-- Software Foundation, either version 2, or at your option any later version.
--
-- This program 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 complete details.
--
------------------------------------------------------------------------------
-- Module Name: pdp11_decode - syn
-- Description: pdp11: instruction decoder
--
-- Dependencies: -
-- Test bench: tb/tb_pdp11_core (implicit)
-- Target Devices: generic
-- Tool versions: xst 8.2, 9.1, 9.2, 13.1; ghdl 0.18-0.29
-- Revision History:
-- Date Rev Version Comment
-- 2011-11-18 427 1.0.6 now numeric_std clean
-- 2010-09-18 300 1.0.5 rename (adlm)box->(oalm)unit
-- 2008-11-30 174 1.0.4 BUGFIX: add updt_dstadsrc; set for MFP(I/D)
-- 2008-05-03 143 1.0.3 get fork_srcr,fork_dstr,fork_dsta assign out of if
-- 2008-04-27 139 1.0.2 BUGFIX: mtp now via do_fork_op; is_dsta logic mods
-- 2007-06-14 56 1.0.1 Use slvtypes.all
-- 2007-05-12 26 1.0 Initial version
------------------------------------------------------------------------------
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use work.slvtypes.all;
use work.pdp11.all;
-- ----------------------------------------------------------------------------
entity pdp11_decode is -- instruction decoder
port (
IREG : in slv16; -- input instruction word
STAT : out decode_stat_type -- status output
);
end pdp11_decode;
architecture syn of pdp11_decode is
begin
proc_idecode: process (IREG)
alias OPCODE : slv4 is IREG(15 downto 12); -- basic opcode (upper 4 bits)
alias OPPRIM : slv3 is IREG(14 downto 12); -- basic opcode without B bit
alias OPBYTE : slbit is IREG(15); -- byte flag of basic opcode
alias OPEXT1 : slv3 is IREG(11 downto 9); -- extended opcode, part 1
alias OPEXT2 : slv3 is IREG(8 downto 6); -- extended opcode, part 2
alias OPEXT3 : slv3 is IREG(5 downto 3); -- extended opcode, part 3
alias OPEXT4 : slv3 is IREG(2 downto 0); -- extended opcode, part 4
alias SRCMODF : slv3 is IREG(11 downto 9); -- src register full mode
alias DSTMODF : slv3 is IREG(5 downto 3); -- dst register full mode
alias SRCMOD : slv2 is IREG(11 downto 10); -- src register mode high
alias SRCDEF : slbit is IREG(9); -- src register mode defered
alias SRCREG : slv3 is IREG(8 downto 6); -- src register number
alias DSTMOD : slv2 is IREG(5 downto 4); -- dst register mode high
alias DSTDEF : slbit is IREG(3); -- dst register mode defered
alias DSTREG : slv3 is IREG(2 downto 0); -- dst register number
variable nstat : decode_stat_type;
variable is_srcr : slbit := '0'; -- source is read
variable is_dstr : slbit := '0'; -- destination is read
variable is_dstm : slbit := '0'; -- destination is modified
variable is_dstw : slbit := '0'; -- destination is written
variable is_srcmode0 : slbit := '0'; -- source is register mode
variable is_dstmode0notpc : slbit := '0'; -- dest. is register mode, not PC
begin
is_srcr := '0';
is_dstr := '0';
is_dstm := '0';
is_dstw := '0';
is_srcmode0 := '0';
is_dstmode0notpc := '0';
nstat.is_dstmode0 := '0';
nstat.is_srcpc := '0';
nstat.is_srcpcmode1 := '0';
nstat.is_dstpc := '0';
nstat.is_dstw_reg := '0';
nstat.is_dstw_pc := '0';
nstat.is_rmwop := '0';
nstat.is_bytop := '0';
nstat.is_res := '1';
nstat.op_rtt := '0';
nstat.op_mov := '0';
nstat.trap_vec := "000";
nstat.force_srcsp := '0';
nstat.updt_dstadsrc := '0';
nstat.aunit_srcmod := c_aunit_mod_pass;
nstat.aunit_dstmod := c_aunit_mod_pass;
nstat.aunit_cimod := c_aunit_mod_pass;
nstat.aunit_cc1op := '0';
nstat.aunit_ccmode := IREG(8 downto 6); -- STATIC
nstat.lunit_func := (others=>'0');
nstat.munit_func := (others=>'0');
nstat.res_sel := c_dpath_res_ounit;
nstat.fork_op := (others=>'0');
nstat.fork_srcr := (others=>'0');
nstat.fork_dstr := (others=>'0');
nstat.fork_dsta := (others=>'0');
nstat.fork_opg := (others=>'0');
nstat.fork_opa := (others=>'0');
nstat.do_fork_op := '0';
nstat.do_fork_srcr := '0';
nstat.do_fork_dstr := '0';
nstat.do_fork_dsta := '0';
nstat.do_fork_opg := '0';
nstat.do_pref_dec := '0';
if SRCMODF = "000" then
is_srcmode0 := '1';
end if;
if DSTMODF = "000" then
nstat.is_dstmode0 := '1';
if DSTREG /= c_gpr_pc then
is_dstmode0notpc := '1';
end if;
end if;
if SRCREG = c_gpr_pc then
nstat.is_srcpc := '1';
if SRCMODF = "001" then
nstat.is_srcpcmode1 := '1';
end if;
end if;
if DSTREG = c_gpr_pc then
nstat.is_dstpc := '1';
end if;
if OPPRIM = "000" then
if OPBYTE='0' and OPEXT1="000" then
if OPEXT2="000" and OPEXT3="000" then -- HALT,...,RTT
nstat.is_res := '0';
case OPEXT4 is
when "000" => -- HALT
nstat.fork_op := c_fork_op_halt;
nstat.do_fork_op := '1';
when "001" => -- WAIT
nstat.fork_op := c_fork_op_wait;
nstat.do_fork_op := '1';
when "010" => -- RTI
nstat.force_srcsp := '1';
nstat.fork_op := c_fork_op_rtti;
nstat.do_fork_op := '1';
when "011" => -- BPT (trap to 14)
nstat.trap_vec := "011";
nstat.fork_op := c_fork_op_trap;
nstat.do_fork_op := '1';
when "100" => -- IOT (trap to 20)
nstat.trap_vec := "100";
nstat.fork_op := c_fork_op_trap;
nstat.do_fork_op := '1';
when "101" => -- RESET
nstat.fork_op := c_fork_op_reset;
nstat.do_fork_op := '1';
when "110" => -- RTT
nstat.op_rtt := '1';
nstat.force_srcsp := '1';
nstat.fork_op := c_fork_op_rtti;
nstat.do_fork_op := '1';
when others =>
nstat.is_res := '1';
end case;
end if;
if OPEXT2 = "001" then -- JMP
nstat.is_res := '0';
nstat.fork_opa := c_fork_opa_jmp;
nstat.do_fork_dsta := '1';
end if;
if OPEXT2 = "010" then
if OPEXT3 = "000" then -- RTS
nstat.is_res := '0';
nstat.force_srcsp := '1';
nstat.fork_op := c_fork_op_rts;
nstat.do_fork_op := '1';
end if;
if OPEXT3 = "011" then -- SPL
nstat.is_res := '0';
nstat.fork_op := c_fork_op_spl;
nstat.do_fork_op := '1';
end if;
end if;
if OPEXT2 = "010" then
if OPEXT3(2) = '1' then -- SEx/CLx
nstat.is_res := '0';
nstat.fork_op := c_fork_op_mcc;
nstat.do_fork_op := '1';
--!!!nstat.do_pref_dec := '1'; --??? ensure ireg_we ....
end if;
end if;
if OPEXT2 = "011" then -- SWAP
nstat.is_res := '0';
is_dstm := '1';
nstat.fork_opg := c_fork_opg_gen;
nstat.do_fork_opg := '1';
nstat.do_pref_dec := is_dstmode0notpc;
nstat.lunit_func := c_lunit_func_swap;
nstat.res_sel := c_dpath_res_lunit;
end if;
end if; -- OPBYTE='0' and OPEXT1="000"
if OPEXT1(2)='0' and -- BR class instructions
((OPBYTE='0' and OPEXT2(2)='1') or -- BR
(OPBYTE='0' and (OPEXT1(0)='1' or OPEXT1(1)='1')) or -- BNE,..,BLE
OPBYTE='1') then -- BPL,..,BCS
nstat.is_res := '0';
nstat.fork_op := c_fork_op_br;
nstat.do_fork_op := '1';
end if;
if OPBYTE='0' and OPEXT1="100" then -- JSR
nstat.is_res := '0';
nstat.fork_opa := c_fork_opa_jsr;
nstat.do_fork_dsta := '1';
end if;
if OPBYTE='1' and OPEXT1="100" then -- EMT, TRAP
nstat.is_res := '0';
if OPEXT2(2) = '0' then -- EMT (trap tp 30)
nstat.trap_vec := "110";
else -- TRAP (trap to 34)
nstat.trap_vec := "111";
end if;
nstat.fork_op := c_fork_op_trap;
nstat.do_fork_op := '1';
end if;
if OPEXT1 = "101" then -- CLR(B),...,TST(B)
nstat.is_res := '0';
nstat.res_sel := c_dpath_res_aunit;
if OPBYTE = '1' then
nstat.is_bytop := '1';
end if;
nstat.aunit_cc1op := '1';
case OPEXT2 is
when "000" => -- CLR: 0 + 0 + 0 (0)
is_dstw := '1';
nstat.aunit_srcmod := c_aunit_mod_zero;
nstat.aunit_dstmod := c_aunit_mod_zero;
nstat.aunit_cimod := c_aunit_mod_zero;
when "001" => -- COM: 0 + ~DST + 0 (~dst)
is_dstm := '1';
nstat.aunit_srcmod := c_aunit_mod_zero;
nstat.aunit_dstmod := c_aunit_mod_inv;
nstat.aunit_cimod := c_aunit_mod_zero;
when "010" => -- INC: 0 + DST + 1 (dst+1)
is_dstm := '1';
nstat.aunit_srcmod := c_aunit_mod_zero;
nstat.aunit_dstmod := c_aunit_mod_pass;
nstat.aunit_cimod := c_aunit_mod_one;
when "011" => -- DEC: ~0 + DST + 0 (dst-1)
is_dstm := '1';
nstat.aunit_srcmod := c_aunit_mod_one;
nstat.aunit_dstmod := c_aunit_mod_pass;
nstat.aunit_cimod := c_aunit_mod_zero;
when "100" => -- NEG: 0 + ~DST + 1 (-dst)
is_dstm := '1';
nstat.aunit_srcmod := c_aunit_mod_zero;
nstat.aunit_dstmod := c_aunit_mod_inv;
nstat.aunit_cimod := c_aunit_mod_one;
when "101" => -- ADC: 0 + DST + CI (dst+ci)
is_dstm := '1';
nstat.aunit_srcmod := c_aunit_mod_zero;
nstat.aunit_dstmod := c_aunit_mod_pass;
nstat.aunit_cimod := c_aunit_mod_pass;
when "110" => -- SBC: ~0 + DST + ~CI (dst-ci)
is_dstm := '1';
nstat.aunit_srcmod := c_aunit_mod_one;
nstat.aunit_dstmod := c_aunit_mod_pass;
nstat.aunit_cimod := c_aunit_mod_inv;
when "111" => -- TST: 0 + DST + 0 (dst)
is_dstr := '1';
nstat.aunit_srcmod := c_aunit_mod_zero;
nstat.aunit_dstmod := c_aunit_mod_pass;
nstat.aunit_cimod := c_aunit_mod_zero;
when others => null;
end case;
nstat.fork_opg := c_fork_opg_gen;
nstat.do_fork_opg := '1';
nstat.do_pref_dec := is_dstmode0notpc;
end if;
if OPEXT1 = "110" then
if OPEXT2(2) = '0' then -- ROR(B),...,ASL(B)
nstat.is_res := '0';
is_dstm := '1';
nstat.fork_opg := c_fork_opg_gen;
nstat.do_fork_opg := '1';
nstat.do_pref_dec := is_dstmode0notpc;
if OPBYTE = '1' then
nstat.is_bytop := '1';
end if;
nstat.res_sel := c_dpath_res_lunit;
case OPEXT2(1 downto 0) is
when "00" => -- ROR
nstat.lunit_func := c_lunit_func_ror;
when "01" => -- ROL
nstat.lunit_func := c_lunit_func_rol;
when "10" => -- ASR
nstat.lunit_func := c_lunit_func_asr;
when "11" => -- ASL
nstat.lunit_func := c_lunit_func_asl;
when others => null;
end case;
end if;
if OPBYTE='0' and OPEXT2="100" then -- MARK
nstat.is_res := '0';
nstat.fork_op := c_fork_op_mark;
nstat.do_fork_op := '1';
end if;
if OPEXT2 = "101" then -- MFP(I/D)
nstat.is_res := '0';
nstat.force_srcsp := '1';
if DSTREG = c_gpr_sp then -- is dst reg == sp ?
nstat.updt_dstadsrc := '1'; -- ensure DSRC update in dsta flow
end if;
nstat.res_sel := c_dpath_res_ounit;
if nstat.is_dstmode0 = '1' then
nstat.fork_opa := c_fork_opa_mfp_reg;
else
nstat.fork_opa := c_fork_opa_mfp_mem;
end if;
nstat.do_fork_dsta := '1';
end if;
if OPEXT2 = "110" then -- MTP(I/D)
nstat.is_res := '0';
nstat.force_srcsp := '1';
nstat.res_sel := c_dpath_res_ounit;
nstat.fork_opa := c_fork_opa_mtp;
nstat.fork_op := c_fork_op_mtp;
nstat.do_fork_op := '1';
end if;
if OPBYTE='0' and OPEXT2="111" then -- SXT
nstat.is_res := '0';
is_dstw := '1';
nstat.fork_opg := c_fork_opg_gen;
nstat.do_fork_opg := '1';
nstat.do_pref_dec := is_dstmode0notpc;
nstat.lunit_func := c_lunit_func_sxt;
nstat.res_sel := c_dpath_res_lunit;
end if;
end if;
end if; -- OPPRIM="000"
if OPPRIM/="000" and OPPRIM/="111" then
nstat.is_res := '0';
case OPPRIM is
when "001" => -- MOV
is_srcr := '1';
is_dstw := '1';
nstat.op_mov := '1';
nstat.lunit_func := c_lunit_func_mov;
nstat.res_sel := c_dpath_res_lunit;
nstat.is_bytop := OPBYTE;
when "010" => -- CMP
is_srcr := '1';
is_dstr := '1';
nstat.res_sel := c_dpath_res_aunit;
nstat.aunit_srcmod := c_aunit_mod_pass;
nstat.aunit_dstmod := c_aunit_mod_inv;
nstat.aunit_cimod := c_aunit_mod_one;
nstat.is_bytop := OPBYTE;
when "011" => -- BIT
is_srcr := '1';
is_dstr := '1';
nstat.lunit_func := c_lunit_func_bit;
nstat.res_sel := c_dpath_res_lunit;
nstat.is_bytop := OPBYTE;
when "100" => -- BIC
is_srcr := '1';
is_dstm := '1';
nstat.lunit_func := c_lunit_func_bic;
nstat.res_sel := c_dpath_res_lunit;
nstat.is_bytop := OPBYTE;
when "101" => -- BIS
is_srcr := '1';
is_dstm := '1';
nstat.lunit_func := c_lunit_func_bis;
nstat.res_sel := c_dpath_res_lunit;
nstat.is_bytop := OPBYTE;
when "110" =>
is_srcr := '1';
is_dstm := '1';
nstat.res_sel := c_dpath_res_aunit;
if OPBYTE = '0' then -- ADD
nstat.aunit_srcmod := c_aunit_mod_pass;
nstat.aunit_dstmod := c_aunit_mod_pass;
nstat.aunit_cimod := c_aunit_mod_zero;
else -- SUB
nstat.aunit_srcmod := c_aunit_mod_inv;
nstat.aunit_dstmod := c_aunit_mod_pass;
nstat.aunit_cimod := c_aunit_mod_one;
end if;
when others => null;
end case;
nstat.fork_opg := c_fork_opg_gen;
nstat.do_fork_opg := '1';
nstat.do_pref_dec := is_srcmode0 and is_dstmode0notpc;
end if;
if OPBYTE='0' and OPPRIM="111" then
case OPEXT1 is
when "000" => -- MUL
nstat.is_res := '0';
is_dstr := '1';
nstat.munit_func := c_munit_func_mul;
nstat.res_sel := c_dpath_res_munit;
nstat.fork_opg := c_fork_opg_mul;
nstat.do_fork_opg := '1';
when "001" => -- DIV
nstat.is_res := '0';
is_dstr := '1';
nstat.munit_func := c_munit_func_div;
nstat.res_sel := c_dpath_res_munit;
nstat.fork_opg := c_fork_opg_div;
nstat.do_fork_opg := '1';
when "010" => -- ASH
nstat.is_res := '0';
is_dstr := '1';
nstat.munit_func := c_munit_func_ash;
nstat.res_sel := c_dpath_res_munit;
nstat.fork_opg := c_fork_opg_ash;
nstat.do_fork_opg := '1';
when "011" => -- ASHC
nstat.is_res := '0';
is_dstr := '1';
nstat.munit_func := c_munit_func_ashc;
nstat.res_sel := c_dpath_res_munit;
nstat.fork_opg := c_fork_opg_ashc;
nstat.do_fork_opg := '1';
when "100" => -- XOR
nstat.is_res := '0';
is_dstm := '1';
nstat.lunit_func := c_lunit_func_xor;
nstat.res_sel := c_dpath_res_lunit;
nstat.fork_opg := c_fork_opg_gen;
nstat.do_fork_opg := '1';
nstat.do_pref_dec := is_dstmode0notpc;
when "111" => -- SOB: SRC + ~0 + 0 (src-1)
nstat.is_res := '0';
nstat.aunit_srcmod := c_aunit_mod_pass;
nstat.aunit_dstmod := c_aunit_mod_one;
nstat.aunit_cimod := c_aunit_mod_zero;
nstat.res_sel := c_dpath_res_aunit;
nstat.fork_op := c_fork_op_sob;
nstat.do_fork_op := '1';
when others => null;
end case;
end if;
if OPBYTE='1' and OPPRIM="111" then -- FPU
nstat.is_res := '1'; -- ??? FPU not yet handled
end if;
case SRCMOD is
when "00" => nstat.fork_srcr := c_fork_srcr_def;
when "01" => nstat.fork_srcr := c_fork_srcr_inc;
when "10" => nstat.fork_srcr := c_fork_srcr_dec;
when "11" => nstat.fork_srcr := c_fork_srcr_ind;
when others => null;
end case;
if is_srcr='1' and SRCMODF /="000" then
nstat.do_fork_srcr := '1';
end if;
case DSTMOD is
when "00" => nstat.fork_dstr := c_fork_dstr_def;
when "01" => nstat.fork_dstr := c_fork_dstr_inc;
when "10" => nstat.fork_dstr := c_fork_dstr_dec;
when "11" => nstat.fork_dstr := c_fork_dstr_ind;
when others => null;
end case;
if (is_dstr or is_dstm)='1' and nstat.is_dstmode0='0' then
nstat.do_fork_dstr := '1';
end if;
if is_dstw='1' and nstat.is_dstmode0='0' then
case DSTMOD is
when "00" => nstat.fork_opg := c_fork_opg_wdef;
when "01" => nstat.fork_opg := c_fork_opg_winc;
when "10" => nstat.fork_opg := c_fork_opg_wdec;
when "11" => nstat.fork_opg := c_fork_opg_wind;
when others => null;
end case;
end if;
if is_dstm='1' and nstat.is_dstmode0='0' then
nstat.is_rmwop := '1';
end if;
case DSTMOD is
when "00" => nstat.fork_dsta := c_fork_dsta_def;
when "01" => nstat.fork_dsta := c_fork_dsta_inc;
when "10" => nstat.fork_dsta := c_fork_dsta_dec;
when "11" => nstat.fork_dsta := c_fork_dsta_ind;
when others => null;
end case;
if (is_dstw or is_dstm)='1' and nstat.is_dstmode0='1' then
nstat.is_dstw_reg := '1';
if DSTREG = c_gpr_pc then
nstat.is_dstw_pc := '1'; --??? hack rename -> is_dstw_pc
end if;
end if;
STAT <= nstat;
end process proc_idecode;
end syn;
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