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Gehstock.Mist_FPGA/common/IO/t48_ip/p2.vhd
Marcel 462f0490bd add Commen Units
2019-07-22 23:42:05 +02:00

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-------------------------------------------------------------------------------
--
-- The Port 2 unit.
-- Implements the Port 2 logic.
--
-- $Id: p2.vhd,v 1.6 2004/07/11 16:51:33 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.word_t;
use work.t48_pack.nibble_t;
entity p2 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_p2_i : in boolean;
write_exp_i : in boolean;
read_p2_i : in boolean;
read_reg_i : in boolean;
read_exp_i : in boolean;
-- Port 2 Interface -------------------------------------------------------
output_pch_i : in boolean;
output_exp_i : in boolean;
pch_i : in nibble_t;
p2_i : in word_t;
p2_o : out word_t;
p2_low_imp_o : out std_logic
);
end p2;
use work.t48_pack.clk_active_c;
use work.t48_pack.res_active_c;
use work.t48_pack.bus_idle_level_c;
architecture rtl of p2 is
-- the port output register
signal p2_q : word_t;
-- the low impedance marker
signal low_imp_q : std_logic;
-- the expander register
signal exp_q : nibble_t;
begin
-----------------------------------------------------------------------------
-- Process p2_regs
--
-- Purpose:
-- Implements the port output and expander registers.
--
p2_regs: process (res_i, clk_i)
begin
if res_i = res_active_c then
p2_q <= (others => '1');
low_imp_q <= '0';
exp_q <= (others => '0');
elsif clk_i'event and clk_i = clk_active_c then
if en_clk_i then
if write_p2_i then
p2_q <= data_i;
low_imp_q <= '1';
else
low_imp_q <= '0';
end if;
if write_exp_i then
exp_q <= data_i(exp_q'range);
end if;
end if;
end if;
end process p2_regs;
--
-----------------------------------------------------------------------------
-----------------------------------------------------------------------------
-- Process p2_port
--
-- Purpose:
-- Generates the output byte vector for Port 2.
--
p2_port: process (p2_q,
exp_q,
output_exp_i,
pch_i,
output_pch_i)
begin
p2_o <= p2_q;
if output_exp_i then
p2_o(nibble_t'range) <= exp_q;
end if;
if output_pch_i then
p2_o(nibble_t'range) <= pch_i;
end if;
end process p2_port;
--
-----------------------------------------------------------------------------
-----------------------------------------------------------------------------
-- Process p2_data
--
-- Purpose:
-- Generates the T48 bus data.
--
p2_data: process (read_p2_i,
p2_i,
read_reg_i,
p2_q,
read_exp_i)
begin
data_o <= (others => bus_idle_level_c);
if read_p2_i then
if read_reg_i then
data_o <= p2_q;
elsif read_exp_i then
data_o <= "0000" & p2_i(nibble_t'range);
else
data_o <= p2_i;
end if;
end if;
end process p2_data;
--
-----------------------------------------------------------------------------
-----------------------------------------------------------------------------
-- Output Mapping.
-----------------------------------------------------------------------------
p2_low_imp_o <= low_imp_q;
end rtl;
-------------------------------------------------------------------------------
-- File History:
--
-- $Log: p2.vhd,v $
-- Revision 1.6 2004/07/11 16:51:33 arniml
-- cleanup copyright notice
--
-- Revision 1.5 2004/05/17 13:52:46 arniml
-- Fix bug "ANL and ORL to P1/P2 read port status instead of port output register"
--
-- Revision 1.4 2004/04/24 23:44:25 arniml
-- move from std_logic_arith to numeric_std
--
-- Revision 1.3 2004/03/29 19:39:58 arniml
-- rename pX_limp to pX_low_imp
--
-- Revision 1.2 2004/03/28 13:11:43 arniml
-- rework Port 2 expander handling
--
-- Revision 1.1 2004/03/23 21:31:53 arniml
-- initial check-in
--
-------------------------------------------------------------------------------
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