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[/] [open8_urisc/] [trunk/] [VHDL/] [o8_gpout.vhd] - Rev 175
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-- Copyright (c)2013 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_gpout -- Description: Provides a single 8-bit GP output register with selectable -- : tri-state control. -- Notes : Requires 1 bit from the address bus (two locations). -- : Sequential instantiations should be separated by 2. library ieee; use ieee.std_logic_1164.all; library work; use work.open8_pkg.all; entity o8_gpout is generic( Default_Out : DATA_TYPE := x"00"; Default_En : DATA_TYPE := x"00"; Disable_Tristate : boolean := false; Reset_Level : std_logic; Address : ADDRESS_TYPE ); port( Clock : in std_logic; Reset : in std_logic; -- Bus_Address : in ADDRESS_TYPE; Wr_Enable : in std_logic; Wr_Data : in DATA_TYPE; Rd_Enable : in std_logic; Rd_Data : out DATA_TYPE; -- GPO : out DATA_TYPE ); end entity; architecture behave of o8_gpout is constant User_Addr : std_logic_vector(15 downto 1) := Address(15 downto 1); alias Comp_Addr is Bus_Address(15 downto 1); alias Reg_Addr is Bus_Address(0); signal Reg_Sel : std_logic; signal Addr_Match : std_logic; signal Wr_En : std_logic; signal Wr_Data_q : DATA_TYPE; signal Rd_En : std_logic; signal User_Out : DATA_TYPE; signal User_En : DATA_TYPE; begin Addr_Match <= '1' when Comp_Addr = User_Addr else '0'; io_reg: process( Clock, Reset ) begin if( Reset = Reset_Level )then Reg_Sel <= '0'; Wr_En <= '0'; Wr_Data_q <= x"00"; Rd_En <= '0'; Rd_Data <= x"00"; User_Out <= Default_Out; if( not Disable_Tristate)then User_En <= Default_En; end if; elsif( rising_edge( Clock ) )then Reg_Sel <= Reg_Addr; Wr_En <= Addr_Match and Wr_Enable; Wr_Data_q <= Wr_Data; if( Wr_En = '1' )then if( Disable_Tristate )then User_Out <= Wr_Data_q; else if( Reg_Sel = '0' )then User_Out <= Wr_Data_q; else User_En <= Wr_Data_q; end if; end if; end if; Rd_Data <= (others => '0'); Rd_En <= Addr_Match and Rd_Enable; if( Rd_En = '1' )then Rd_Data <= User_Out; if( (Reg_Sel = '1') and (not Disable_Tristate) )then Rd_Data <= User_En; end if; end if; end if; end process; No_Tristates: if( Disable_Tristate )generate GPO <= User_Out; end generate; Tristates: if( not Disable_Tristate )generate Output_Ctl_proc: process( User_Out, User_En ) begin for i in 0 to 7 loop GPO(i) <= 'Z'; if( User_En(i) = '1' )then GPO(i) <= User_Out(i); end if; end loop; end process; end generate; end architecture;
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