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i8244_major_obj.vhd
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i8244_major_obj.vhd
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-------------------------------------------------------------------------------
--
-- i8244 Video Display Controller
--
-- $Id: i8244_major_obj.vhd,v 1.8 2007/02/05 22:08:59 arnim Exp $
--
-- Major Display Object
--
-------------------------------------------------------------------------------
--
-- Copyright (c) 2007, Arnim Laeuger (arnim.laeuger@gmx.net)
--
-- 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.
--
-------------------------------------------------------------------------------
library ieee;
use ieee.std_logic_1164.all;
use work.i8244_pack.pos_t;
use work.i8244_pack.col_attr_t;
use work.i8244_major_pack.all;
entity i8244_major_obj is
port (
clk_i : in std_logic;
clk_en_i : in boolean;
res_i : in boolean;
hpos_i : in pos_t;
vpos_i : in pos_t;
vstop_i : in boolean;
hstop_i : in boolean;
obj_i : in major_obj_t;
vhmatch_o : out boolean;
lss_o : out lss_t;
col_attr_o : out col_attr_t
);
end i8244_major_obj;
library ieee;
use ieee.numeric_std.all;
use work.i8244_pack.byte_t;
architecture rtl of i8244_major_obj is
signal vactive_s,
vactive_q : boolean;
signal hactive_s,
hactive_q : boolean;
signal vhmatch_s : boolean;
begin
-----------------------------------------------------------------------------
-- Process seq
--
-- Purpose:
-- Implements the sequential elements of a major object.
--
seq: process (clk_i, res_i)
begin
if res_i then
vactive_q <= false;
hactive_q <= false;
elsif rising_edge(clk_i) then
if clk_en_i then
-- default update
vactive_q <= vactive_s;
hactive_q <= hactive_s;
if vactive_q and hactive_q then
if vstop_i then
-- char is finished
vactive_q <= false;
end if;
if hstop_i and not vhmatch_s then
-- current line is finished
hactive_q <= false;
end if;
end if;
end if;
end if;
end process seq;
--
-----------------------------------------------------------------------------
-----------------------------------------------------------------------------
-- Process comb
--
-- Purpose:
-- Implements the combinational logic of a major object:
-- * vertical CAM comparison
-- * horizontal CAM comparison
--
comb: process (hpos_i, vpos_i,
obj_i,
vactive_q, hactive_q)
variable vactive_v,
hactive_v : boolean;
begin
-- default assignments
vhmatch_s <= false;
vactive_v := vactive_q;
hactive_v := hactive_q;
-- vertical CAM comparison ------------------------------------------------
if vpos_i(pos_t'high downto 1) =
unsigned(obj_i.cam_y(byte_t'high downto 1)) and
hpos_i = 0 then
vactive_v := true;
end if;
-- horizontal CAM comparison ----------------------------------------------
if vactive_v and
hpos_i(pos_t'high downto 1) =
unsigned(obj_i.cam_x) then
hactive_v := true;
vhmatch_s <= true;
end if;
vactive_s <= vactive_v;
hactive_s <= hactive_v;
end process comb;
--
-----------------------------------------------------------------------------
-----------------------------------------------------------------------------
-- Process output
--
-- Purpose:
-- Generates the output signals.
-- Per default, they are inactive and only when a line of this object
-- is displayed, they carry information.
--
output: process (vactive_q, hactive_q,
vhmatch_s,
hstop_i,
obj_i)
begin
-- default (inactive state) assignemnts
lss_o <= (others => '0');
col_attr_o <= (others => '0');
-- drive active data when
-- * V/H match occurs
-- * this object is actively displaying a line and
-- no horizontal stop has been signalled
if vhmatch_s or
(vactive_q and hactive_q and not hstop_i) then
-- stop LSS immediately to prevent overlap with next character
-- when (pre)fetching ROM data
lss_o <= obj_i.attr.lss;
end if;
if vhmatch_s or
(vactive_q and hactive_q) then
col_attr_o <= obj_i.attr.col;
end if;
end process output;
--
-----------------------------------------------------------------------------
vhmatch_o <= vhmatch_s;
end rtl;