trans_arb.vhd

-- trans_arb
--
-- Arbitrates access to transactor by multiple packet buffers
--
-- Dave Newbold, February 2013
--
-- $Id$

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

use work.ipbus_trans_decl.all;

entity trans_arb is
  generic(NSRC: positive);
  port(
    clk: in std_logic; 
    rst: in std_logic;
    buf_in: in ipbus_trans_in_array(NSRC-1 downto 0);
    buf_out: out ipbus_trans_out_array(NSRC-1 downto 0);
    trans_out: out ipbus_trans_in;
    trans_in: in ipbus_trans_out
  );

end trans_arb;

architecture rtl of trans_arb is
  
    signal src: unsigned(1 downto 0); -- Up to four ports...
    signal sel: integer := 0;
    signal busy: std_logic;
  
begin

    sel <= to_integer(src);

    process(clk)
    begin
        if rising_edge(clk) then
            if rst = '1' then
                busy <= '0';
                src <= (others => '0');
            elsif busy = '0' then
                if buf_in(sel).pkt_rdy /= '1' then
                    if src /= (NSRC - 1) then
                        src <= src + 1;
                    else
                        src <= (others => '0');
                    end if;
                else
                    busy <= '1';
                end if;
            elsif trans_in.pkt_done = '1' then
                busy <= '0';
            end if;
        end if;
    end process;

    trans_out.pkt_rdy <= buf_in(sel).pkt_rdy;
    trans_out.rdata <= buf_in(sel).rdata;
    trans_out.busy <= buf_in(sel).busy;

  busgen: for i in NSRC - 1 downto 0 generate
  begin
    buf_out(i).pkt_done <= trans_in.pkt_done when sel = i else '0';
    buf_out(i).wdata <= trans_in.wdata;
    buf_out(i).waddr <= trans_in.waddr;
    buf_out(i).raddr <= trans_in.raddr;
    buf_out(i).we <= trans_in.we when sel = i else '0';      
  end generate;
  
end rtl;