Subversion Repositories wb_tk

--
--  Wishbone bus toolkit.
--
--  (c) Copyright Andras Tantos <andras_tantos@yahoo.com> 2001/03/31
--  This code is distributed under the terms and conditions of the GNU General Public Lince.
--
--
-- ELEMENTS:
--   wb_out_reg: Wishbone bus compatible output register.
 
-------------------------------------------------------------------------------
--
--  wb_out_reg
--
-------------------------------------------------------------------------------
 
library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.STD_LOGIC_UNSIGNED.all;
 
library wb_tk;
use wb_tk.technology.all;
 
entity wb_in_reg is
    generic (
        reg_width : positive := 8;
        dat_width: positive := 8;
        offset: integer := 0
    );
    port (
        clk_i: in std_logic;
        rst_i: in std_logic;
 
        cyc_i: in std_logic := '1';
        stb_i: in std_logic;
        sel_i: in std_logic_vector (max2((dat_width/8)-1,0) downto 0) := (others => '1');
        we_i: in std_logic;
        ack_o: out std_logic;
        ack_oi: in std_logic := '-';
        adr_i: in std_logic_vector (size2bits((reg_width+offset+dat_width-1)/dat_width)-1 downto 0) := (others => '0');
        dat_oi: in std_logic_vector (dat_width-1 downto 0) := (others => '-');
        dat_o: out std_logic_vector (dat_width-1 downto 0);
        i: in std_logic_vector (reg_width-1 downto 0)
    );
end wb_in_reg;
 
architecture wb_in_reg of wb_in_reg is
    signal content : std_logic_vector (reg_width-1 downto 0);
    signal word_en: std_logic_vector ((reg_width / dat_width)-1 downto 0);
begin
    -- address demux
    adr_demux: process (adr_i)
    begin
        word_en <= (others => '0');
        --:::TA Possible problem: index range can be out of bounds at least accroding to XST
        word_en(to_integer(adr_i)) <= '1';
    end process;
 
    -- output bus handling with logic
    gen_dat_o: process(
        dat_oi, we_i, stb_i, content, word_en, cyc_i, sel_i
    )
        variable rd_sel: std_logic;
        variable dat_idx: integer;
    begin
        rd_sel := cyc_i and stb_i and not we_i;
 
        -- The default is the input, we'll override it if we need to
        for i in dat_o'RANGE loop
            dat_o(i) <= dat_oi(i);
        end loop;
        for i in content'RANGE loop
            dat_idx := (i+offset) mod dat_width;
            if (
--              (sel_i((i/8) mod (dat_width/8)) = '1') and
                (word_en(i/dat_width) = '1') and
                (rd_sel = '1')
            ) then
--              dat_o(dat_idx) <= (dat_oi(dat_idx) and not rd_sel) or (content(i) and rd_sel);
                dat_o(dat_idx) <= content(i);
            end if;
        end loop;
    end process;
--    dat_o <= dat_oi;
 
    -- this item never generates any wait-states
    ack_o <= stb_i or ack_oi;
 
    reg: process
    begin
        wait until clk_i'EVENT and clk_i='1';
        content <=  i;
    end process;
end wb_in_reg;