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[/] [System09/] [tags/] [V10/] [rtl/] [vhdl/] [datram.vhd] - Rev 198
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--===========================================================================-- -- -- S Y N T H E Z I A B L E Dynamic Address Translation Registers -- -- www.OpenCores.Org - December 2002 -- This core adheres to the GNU public license -- -- File name : datram.vhd -- -- entity name : dat_ram -- -- Purpose : Implements a Dynamic Address Translation RAM module -- Maps the high order 4 address bits to 8 address lines -- extending the memory addressing range to 1 Mbytes -- Memory segments are mapped on 4 KByte boundaries -- The DAT registers map to the top of memory -- ($FFF0 - $FFFF) and are write only so can map over ROM. -- Since the DAT is not supported by SWTBUG for the 6800, -- the resgisters reset state map the bottom 64K of RAM. -- -- Dependencies : ieee.Std_Logic_1164 -- ieee.std_logic_unsigned -- -- Author : John E. Kent -- --===========================================================================---- -- -- Revision History: -- -- Date Revision Author -- 10 Nov 2002 0.1 John Kent -- library ieee; use ieee.std_logic_1164.all; use ieee.std_logic_unsigned.all; entity dat_ram is port ( clk : in std_logic; rst : in std_logic; cs : in std_logic; rw : in std_logic; addr_hi : in std_logic_vector(3 downto 0); addr_lo : in std_logic_vector(3 downto 0); data_in : in std_logic_vector(7 downto 0); data_out : out std_logic_vector(7 downto 0)); end; architecture datram_arch of dat_ram is signal dat_reg0 : std_logic_vector(7 downto 0); signal dat_reg1 : std_logic_vector(7 downto 0); signal dat_reg2 : std_logic_vector(7 downto 0); signal dat_reg3 : std_logic_vector(7 downto 0); signal dat_reg4 : std_logic_vector(7 downto 0); signal dat_reg5 : std_logic_vector(7 downto 0); signal dat_reg6 : std_logic_vector(7 downto 0); signal dat_reg7 : std_logic_vector(7 downto 0); signal dat_reg8 : std_logic_vector(7 downto 0); signal dat_reg9 : std_logic_vector(7 downto 0); signal dat_reg10 : std_logic_vector(7 downto 0); signal dat_reg11 : std_logic_vector(7 downto 0); signal dat_reg12 : std_logic_vector(7 downto 0); signal dat_reg13 : std_logic_vector(7 downto 0); signal dat_reg14 : std_logic_vector(7 downto 0); signal dat_reg15 : std_logic_vector(7 downto 0); begin --------------------------------- -- -- Write DAT RAM -- --------------------------------- dat_write : process( clk, rst, addr_lo, cs, rw, data_in ) begin if clk'event and clk = '0' then if rst = '1' then dat_reg0 <= "00000000"; dat_reg1 <= "00000001"; dat_reg2 <= "00000010"; dat_reg3 <= "00000011"; dat_reg4 <= "00000100"; dat_reg5 <= "00000101"; dat_reg6 <= "00000110"; dat_reg7 <= "00000111"; dat_reg8 <= "00001000"; dat_reg9 <= "00001001"; dat_reg10 <= "00001010"; dat_reg11 <= "00001011"; dat_reg12 <= "00001100"; dat_reg13 <= "00001101"; dat_reg14 <= "00001110"; dat_reg15 <= "00001111"; else if cs = '1' and rw = '0' then case addr_lo is when "0000" => dat_reg0 <= data_in; when "0001" => dat_reg1 <= data_in; when "0010" => dat_reg2 <= data_in; when "0011" => dat_reg3 <= data_in; when "0100" => dat_reg4 <= data_in; when "0101" => dat_reg5 <= data_in; when "0110" => dat_reg6 <= data_in; when "0111" => dat_reg7 <= data_in; when "1000" => dat_reg8 <= data_in; when "1001" => dat_reg9 <= data_in; when "1010" => dat_reg10 <= data_in; when "1011" => dat_reg11 <= data_in; when "1100" => dat_reg12 <= data_in; when "1101" => dat_reg13 <= data_in; when "1110" => dat_reg14 <= data_in; when "1111" => dat_reg15 <= data_in; when others => null; end case; end if; end if; end if; end process; dat_read : process( addr_hi, dat_reg0, dat_reg1, dat_reg2, dat_reg3, dat_reg4, dat_reg5, dat_reg6, dat_reg7, dat_reg8, dat_reg9, dat_reg10, dat_reg11, dat_reg12, dat_reg13, dat_reg14, dat_reg15 ) begin case addr_hi is when "0000" => data_out <= dat_reg0; when "0001" => data_out <= dat_reg1; when "0010" => data_out <= dat_reg2; when "0011" => data_out <= dat_reg3; when "0100" => data_out <= dat_reg4; when "0101" => data_out <= dat_reg5; when "0110" => data_out <= dat_reg6; when "0111" => data_out <= dat_reg7; when "1000" => data_out <= dat_reg8; when "1001" => data_out <= dat_reg9; when "1010" => data_out <= dat_reg10; when "1011" => data_out <= dat_reg11; when "1100" => data_out <= dat_reg12; when "1101" => data_out <= dat_reg13; when "1110" => data_out <= dat_reg14; when "1111" => data_out <= dat_reg15; when others => null; end case; end process; end datram_arch;
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