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[/] [open8_urisc/] [trunk/] [VHDL/] [o8_gpin.vhd] - Rev 204
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-- Copyright (c)2006, 2016, 2019, 2020 Jeremy Seth Henry -- All rights reserved. -- -- Redistribution and use in source and binary 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 binary 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, -- where applicable (as part of a user interface, debugging port, etc.) -- -- THIS SOFTWARE IS PROVIDED BY JEREMY SETH HENRY ``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 JEREMY SETH HENRY 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. -- -- VHDL Units : o8_gpin -- Description: Provides a single 8-bit input register -- -- Note: Cut the path between GPIN and GPIN_q1 for timing analysis -- -- Revision History -- Author Date Change ------------------ -------- --------------------------------------------------- -- Seth Henry 07/28/11 Design Start -- Seth Henry 12/19/19 Renamed to "o8_gpin" to fit "theme" -- Seth Henry 12/20/19 Added metastability registers library ieee; use ieee.std_logic_1164.all; library work; use work.open8_pkg.all; entity o8_gpin is generic( Reset_Level : std_logic; Address : ADDRESS_TYPE ); port( Clock : in std_logic; Reset : in std_logic; -- Bus_Address : in ADDRESS_TYPE; Rd_Enable : in std_logic; Rd_Data : out DATA_TYPE; -- GPIN : in DATA_TYPE ); end entity; architecture behave of o8_gpin is constant User_Addr : std_logic_vector(15 downto 0) := Address; alias Comp_Addr is Bus_Address(15 downto 0); signal Addr_Match : std_logic; signal Rd_En : std_logic; signal GPIN_q1 : DATA_TYPE; signal GPIN_q2 : DATA_TYPE; signal User_In : DATA_TYPE; begin Addr_Match <= Rd_Enable when Comp_Addr = User_Addr else '0'; io_reg: process( Clock, Reset ) begin if( Reset = Reset_Level )then Rd_En <= '0'; Rd_Data <= OPEN8_NULLBUS; GPIN_q1 <= x"00"; GPIN_q2 <= x"00"; User_In <= x"00"; elsif( rising_edge( Clock ) )then GPIN_q1 <= GPIN; GPIN_q2 <= GPIN_q1; User_In <= GPIN_q2; Rd_Data <= OPEN8_NULLBUS; Rd_En <= Addr_Match; if( Rd_En = '1' )then Rd_Data <= User_In; end if; end if; end process; end architecture;
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