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Gehstock.Mist_FPGA/common/CPU/t48/pmem_ctrl.vhd
Gehstock 3656363a3c Some work on Donkey Kong + Clean up
2020-05-13 15:54:31 +02:00

246 lines
7.8 KiB
VHDL
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-------------------------------------------------------------------------------
--
-- The Program Memory control unit.
-- All operations related to the Program Memory are managed here.
--
-- $Id: pmem_ctrl.vhd,v 1.5 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.pmem_addr_t;
use work.t48_pack.word_t;
use work.t48_pmem_ctrl_pack.pmem_addr_ident_t;
entity t48_pmem_ctrl is
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;
data_o : out word_t;
write_pcl_i : in boolean;
read_pcl_i : in boolean;
write_pch_i : in boolean;
read_pch_i : in boolean;
inc_pc_i : in boolean;
write_pmem_addr_i : in boolean;
addr_type_i : in pmem_addr_ident_t;
read_pmem_i : in boolean;
-- Porgram Memroy Interface -----------------------------------------------
pmem_addr_o : out pmem_addr_t;
pmem_data_i : in word_t
);
end t48_pmem_ctrl;
library ieee;
use ieee.numeric_std.all;
use work.t48_pmem_ctrl_pack.all;
use work.t48_pack.res_active_c;
use work.t48_pack.clk_active_c;
use work.t48_pack.bus_idle_level_c;
use work.t48_pack.pmem_addr_width_c;
use work.t48_pack.dmem_addr_width_c;
use work.t48_pack.page_t;
architecture rtl of t48_pmem_ctrl is
-- implemented counter width of Program Counter
-- the upper bit is only altered by JMP, CALL and RET(R)
subtype pc_count_range_t is natural range pmem_addr_width_c-2 downto 0;
-- the Program Counter
signal program_counter_q : unsigned(pmem_addr_t'range);
-- the Program Memory address
signal pmem_addr_s,
pmem_addr_q : std_logic_vector(pmem_addr_t'range);
begin
-----------------------------------------------------------------------------
-- Process program_counter
--
-- Purpose:
-- Implements the Program Counter.
--
program_counter: process (res_i, clk_i)
begin
if res_i = res_active_c then
program_counter_q <= (others => '0');
pmem_addr_q <= (others => '0');
elsif clk_i'event and clk_i = clk_active_c then
if en_clk_i then
-- parallel load mode
if write_pcl_i then
program_counter_q(data_i'range) <= UNSIGNED(data_i);
elsif write_pch_i then
program_counter_q(pmem_addr_width_c-1 downto data_i'high+1) <=
UNSIGNED(data_i(pmem_addr_width_c - dmem_addr_width_c - 1 downto 0));
elsif inc_pc_i then
-- increment mode
-- the MSB is not modified by linear increments
-- it can only be altered by JMP, CALL or RET(R)
program_counter_q(pc_count_range_t) <=
program_counter_q(pc_count_range_t) + 1;
end if;
-- set pmem address
if write_pmem_addr_i then
pmem_addr_q <= pmem_addr_s;
end if;
end if;
end if;
end process program_counter;
--
-----------------------------------------------------------------------------
-----------------------------------------------------------------------------
-- Process pmem_addr
--
-- Purpose:
-- Multiplex the Program Memory address.
--
pmem_addr: process (program_counter_q,
addr_type_i,
pmem_addr_q,
data_i)
begin
-- default assignment
pmem_addr_s <= STD_LOGIC_VECTOR(program_counter_q);
case addr_type_i is
when PM_PC =>
-- default is ok
null;
when PM_PAGE =>
pmem_addr_s(word_t'range) <= data_i;
-- take page address from program counter
-- => important for JMPP, MOVP!
-- they must wrap to next page when at FF!
when PM_PAGE3 =>
pmem_addr_s(word_t'range) <= data_i;
-- page address is explicitely specified
pmem_addr_s(page_t'range) <= "0011";
when others =>
null;
end case;
end process pmem_addr;
--
-----------------------------------------------------------------------------
-----------------------------------------------------------------------------
-- Process data_output
--
-- Purpose:
-- Multiplex the data bus output.
--
data_output: process (read_pmem_i,
read_pcl_i,
read_pch_i,
pmem_data_i,
program_counter_q)
begin
data_o <= (others => bus_idle_level_c);
if read_pmem_i then
data_o <= pmem_data_i;
elsif read_pcl_i then
data_o <= STD_LOGIC_VECTOR(program_counter_q(data_o'range));
elsif read_pch_i then
data_o(3 downto 0) <= STD_LOGIC_VECTOR(program_counter_q(pmem_addr_width_c-1 downto data_o'high+1));
end if;
end process data_output;
--
-----------------------------------------------------------------------------
-----------------------------------------------------------------------------
-- Output Mapping.
-----------------------------------------------------------------------------
pmem_addr_o <= pmem_addr_q;
end rtl;
-------------------------------------------------------------------------------
-- File History:
--
-- $Log: pmem_ctrl.vhd,v $
-- Revision 1.5 2005/06/11 10:08:43 arniml
-- introduce prefix 't48_' for all packages, entities and configurations
--
-- Revision 1.4 2005/06/08 19:13:53 arniml
-- fix bug report
-- "MSB of Program Counter changed upon PC increment"
--
-- Revision 1.3 2004/07/11 16:51:33 arniml
-- cleanup copyright notice
--
-- Revision 1.2 2004/04/24 23:44:25 arniml
-- move from std_logic_arith to numeric_std
--
-- Revision 1.1 2004/03/23 21:31:53 arniml
-- initial check-in
--
-------------------------------------------------------------------------------
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