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-- $Id: ibdr_dl11.vhd 314 2010-07-09 17:38:41Z mueller $

--

-- Copyright 2008-2010 by Walter F.J. Mueller <W.F.J.Mueller@gsi.de>

--

-- This program is free software; you may redistribute and/or modify it under

-- the terms of the GNU General Public License as published by the Free

-- Software Foundation, either version 2, or at your option any later version.

--

-- This program is distributed in the hope that it will be useful, but

-- WITHOUT ANY WARRANTY, without even the implied warranty of MERCHANTABILITY

-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

-- for complete details.

--

------------------------------------------------------------------------------

-- Module Name:    ibdr_dl11 - syn

-- Description:    ibus dev(rem): DL11-A/B

--

-- Dependencies:   -

-- Test bench:     -

-- Target Devices: generic

-- Tool versions:  xst 8.1, 8.2, 9.1, 9.2, 10.1; ghdl 0.18-0.25

--

-- Synthesized (xst):

-- Date         Rev  ise         Target      flop lutl lutm slic t peri

-- 2009-07-12   233  10.1.03 K39 xc3s1000-4    38  119    0   69 s  6.3

-- 2009-07-11   232  10.1.03 K39 xc3s1000-4    23   61    0   40 s  5.5

--

-- Revision History: 

-- Date         Rev Version  Comment

-- 2010-06-11   303   1.1    use IB_MREQ.racc instead of RRI_REQ

-- 2009-07-12   233   1.0.5  add RESET, CE_USEC port; implement input rate limit

-- 2008-08-22   161   1.0.6  use iblib; add EI_ACK_* to proc_next sens. list

-- 2008-05-09   144   1.0.5  use intreq flop, use EI_ACK

-- 2008-03-22   128   1.0.4  rename xdone -> xval (no functional change)

-- 2008-01-27   115   1.0.3  bugfix: set ilam when rbuf read by cpu;

--                           add xdone and rrdy bits to rri xbuf read

-- 2008-01-20   113   1.0.2  fix maint mode logic (proper double buffer now)

-- 2008-01-20   112   1.0.1  use BRESET

-- 2008-01-05   108   1.0    Initial version 

------------------------------------------------------------------------------

library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_arith.all;

use work.slvtypes.all;

use work.iblib.all;

-- ----------------------------------------------------------------------------

entity ibdr_dl11 is                     -- ibus dev(rem): DL11-A/B

  generic (

    IB_ADDR : slv16 := conv_std_logic_vector(8#177560#,16));

  port (

    CLK : in slbit;                     -- clock

    CE_USEC : in slbit;                 -- usec pulse

    RESET : in slbit;                   -- system reset

    BRESET : in slbit;                  -- ibus reset

    RRI_LAM : out slbit;                -- remote attention

    IB_MREQ : in ib_mreq_type;          -- ibus request

    IB_SRES : out ib_sres_type;         -- ibus response

    EI_REQ_RX : out slbit;              -- interrupt request, receiver

    EI_REQ_TX : out slbit;              -- interrupt request, transmitter

    EI_ACK_RX : in slbit;               -- interrupt acknowledge, receiver

    EI_ACK_TX : in slbit                -- interrupt acknowledge, transmitter

  );

end ibdr_dl11;

architecture syn of ibdr_dl11 is

  constant ibaddr_rcsr : slv2 := "00";  -- rcsr address offset

  constant ibaddr_rbuf : slv2 := "01";  -- rbuf address offset

  constant ibaddr_xcsr : slv2 := "10";  -- xcsr address offset

  constant ibaddr_xbuf : slv2 := "11";  -- xbuf address offset

  subtype  rcsr_ibf_rrlim   is integer range 14 downto 12;

  constant rcsr_ibf_rdone : integer :=  7;

  constant rcsr_ibf_rie :   integer :=  6;

  constant xcsr_ibf_xrdy :  integer :=  7;

  constant xcsr_ibf_xie :   integer :=  6;

  constant xcsr_ibf_xmaint: integer :=  2;

  constant xbuf_ibf_xval :  integer :=  8;

  constant xbuf_ibf_rrdy :  integer :=  9;

  type regs_type is record              -- state registers

    rrlim : slv3;                       -- rcsr: receiver rate limit

    rdone : slbit;                      -- rcsr: receiver done

    rie : slbit;                        -- rcsr: receiver interrupt enable

    rbuf : slv8;                        -- rbuf:

    rval : slbit;                       -- rx rbuf valid

    rintreq : slbit;                    -- rx interrupt request

    rdlybsy : slbit;                    -- rx delay busy

    rdlycnt : slv10;                    -- rx delay counter

    xrdy : slbit;                       -- xcsr: transmitter ready

    xie : slbit;                        -- xcsr: transmitter interrupt enable

    xmaint : slbit;                     -- xcsr: maintenance mode

    xbuf : slv8;                        -- xbuf:

    xintreq : slbit;                    -- tx interrupt request

  end record regs_type;

  constant regs_init : regs_type := (

    (others=>'0'),                      -- rrlim

    '0','0',                            -- rdone, rie

    (others=>'0'),                      -- rbuf

    '0','0','0',                        -- rval,rintreq,rdlybsy

    (others=>'0'),                      -- rdlycnt

    '1',                                -- xrdy !! is set !!

    '0','0',                            -- xie,xmaint

    (others=>'0'),                      -- xbuf

    '0'                                 -- xintreq

  );

  signal R_REGS : regs_type := regs_init;

  signal N_REGS : regs_type := regs_init;

begin

  proc_regs: process (CLK)

  begin

    if CLK'event and CLK='1' then

      if BRESET = '1' then

        R_REGS <= regs_init;

        if RESET = '0' then               -- if RESET=0 we do just an ibus reset

          R_REGS.rrlim   <= N_REGS.rrlim;   -- don't reset rx rate limit

          R_REGS.rdlybsy <= N_REGS.rdlybsy; -- don't reset rx delay busy

          R_REGS.rdlycnt <= N_REGS.rdlycnt; -- don't reset rx delay counter

        end if;

     else

        R_REGS <= N_REGS;

      end if;

    end if;

  end process proc_regs;

  proc_next : process (CE_USEC, R_REGS, IB_MREQ, EI_ACK_RX, EI_ACK_TX)

    variable r : regs_type := regs_init;

    variable n : regs_type := regs_init;

    variable ibsel : slbit := '0';

    variable idout : slv16 := (others=>'0');

    variable ibrd : slbit := '0';

    variable ibw0 : slbit := '0';

    variable ibw1 : slbit := '0';

    variable ilam : slbit := '0';

    variable rdlystart : slbit := '0';

    variable rdlyinit : slv10 := (others=>'0');

  begin

    r := R_REGS;

    n := R_REGS;

    ibsel := '0';

    idout := (others=>'0');

    ibrd  := not IB_MREQ.we;

    ibw0  := IB_MREQ.we and IB_MREQ.be0;

    ibw1  := IB_MREQ.we and IB_MREQ.be1;

    ilam  := '0';

    rdlystart := '0';

    -- ibus address decoder

    if IB_MREQ.req='1' and IB_MREQ.addr(12 downto 3)=IB_ADDR(12 downto 3) then

      ibsel := '1';

    end if;

    -- ibus transactions

    if ibsel = '1' then

      case IB_MREQ.addr(2 downto 1) is

        when ibaddr_rcsr =>             -- RCSR -- receive control status ----

          idout(rcsr_ibf_rdone) := r.rdone;

          idout(rcsr_ibf_rie)   := r.rie;

          if IB_MREQ.racc = '0' then     -- cpu ---------------------

            if ibw0 = '1' then

              n.rie := IB_MREQ.din(rcsr_ibf_rie);

              if IB_MREQ.din(rcsr_ibf_rie) = '1' then

                if r.rdone='1' and r.rie='0' then -- ie set while done=1

                  n.rintreq := '1';               -- request interrupt

                end if;

              else

                n.rintreq := '0';

              end if;

            end if;

          else                          -- rri ---------------------

            idout(rcsr_ibf_rrlim) := r.rrlim;

            if ibw1 = '1' then

              n.rrlim := IB_MREQ.din(rcsr_ibf_rrlim);

            end if;

          end if;

        when ibaddr_rbuf =>             -- RBUF -- receive data buffer -------

          idout(r.rbuf'range)   := r.rbuf;

          if IB_MREQ.racc = '0' then    -- cpu ---------------------

            if ibrd = '1' then

              n.rdone   := '0';           -- clear DONE

              n.rval    := '0';           -- clear rbuf valid

              n.rintreq := '0';           -- clear pending interrupts

              rdlystart := '1';           -- start rx delay counter

              if r.xmaint = '0' then      -- if not in loop-back

                ilam := '1';                -- request rb attention

              end if;

            end if;

          else                          -- rri ---------------------

            if ibw0 = '1' then

              n.rbuf := IB_MREQ.din(n.rbuf'range);

              n.rval := '1';              -- set rbuf valid

              if r.rdlybsy = '0' then     -- if rdly timer not running

                n.rdone := '1';             -- set DONE

                if r.rie = '1' then         -- if rx interrupt enabled

                  n.rintreq := '1';           -- request interrupt

                end if;

              end if;

            end if;

          end if;

        when ibaddr_xcsr =>             -- XCSR -- transmit control status ---

          idout(xcsr_ibf_xrdy)  := r.xrdy;

          idout(xcsr_ibf_xie)   := r.xie;

          idout(xcsr_ibf_xmaint):= r.xmaint;

          if IB_MREQ.racc = '0' then    -- cpu ---------------------

            if ibw0 = '1' then

              n.xie   := IB_MREQ.din(xcsr_ibf_xie);

              if IB_MREQ.din(xcsr_ibf_xie) = '1' then

                if r.xrdy='1' and r.xie='0' then -- ie set while ready=1

                  n.xintreq := '1';               -- request interrupt

                end if;

              else

                n.xintreq := '0';

              end if;

              n.xmaint := IB_MREQ.din(xcsr_ibf_xmaint);

            end if;

          end if;

        when ibaddr_xbuf =>             -- XBUF -- transmit data buffer ------

          if IB_MREQ.racc = '0' then    -- cpu ---------------------

            if ibw0 = '1' then

              n.xbuf := IB_MREQ.din(n.xbuf'range);

              n.xrdy := '0';

              n.xintreq := '0';

              if r.xmaint = '0' then

                ilam := '1';

              end if;

            end if;

          else                          -- rri ---------------------

            idout(r.xbuf'range)  := r.xbuf;

            if r.xmaint = '0' then        -- if not in maintenace mode

              idout(xbuf_ibf_xval) := not r.xrdy;

              idout(xbuf_ibf_rrdy) := not r.rval;

            end if;

            if ibrd = '1' then

              n.xrdy := '1';

              if r.xie = '1' then

                n.xintreq := '1';

              end if;

            end if;

          end if;

        when others => null;

      end case;

    else                                -- if unselected handle loop-back

      if r.xmaint = '1' and               -- if in maintenace mode

          r.xrdy='0' and                  -- and transmit pending

          r.rdone='0' and                 -- and receive buffer empty

          r.rdlybsy='0' then              -- and rdly timer not running

        n.rbuf  := r.xbuf;                  -- copy transmit to receive buffer

        n.xrdy  := '1';                     -- mark transmit done

        n.rdone := '1';                     -- make receive done

        if r.rie = '1' then                 -- if rx interrupt enabled

          n.rintreq := '1';                   -- request it

        end if;

        if r.xie = '1' then                 -- if tx interrupt enabled

          n.xintreq := '1';                   -- request it

        end if;

      end if;

    end if;

    -- other state changes

    rdlyinit := (others=>'0');

    case r.rrlim is

      when "000" => rdlyinit := "0000000000"; -- rlim=0 -> disabled

      when "001" => rdlyinit := "0000000011"; -- rlim=1 -> delay by    3+ usec

      when "010" => rdlyinit := "0000001111"; -- rlim=2 -> delay by   15+ usec

      when "011" => rdlyinit := "0000111111"; -- rlim=3 -> delay by   63+ usec

      when "100" => rdlyinit := "0001111111"; -- rlim=4 -> delay by  127+ usec

      when "101" => rdlyinit := "0011111111"; -- rlim=5 -> delay by  255+ usec

      when "110" => rdlyinit := "0111111111"; -- rlim=6 -> delay by  511+ usec

      when "111" => rdlyinit := "1111111111"; -- rlim=7 -> delay by 1023+ usec

      when others => null;

    end case;

    if rdlystart = '1' then                 -- if rdly timer start requested

      n.rdlycnt := rdlyinit;                  -- init counter

      if r.rrlim /= "000" then                -- rate limiter enabled ?

        n.rdlybsy := '1';                       -- set busy 

      end if;

    elsif CE_USEC = '1' then                -- if end-of-usec

      n.rdlycnt := unsigned(r.rdlycnt) - 1;   -- decrement

      if r.rdlybsy='1' and                   -- if delay busy

          unsigned(r.rdlycnt) = 0 then        --   and counter at zero

        n.rdlybsy := '0';                       -- clear busy

        if n.rval = '1' then                    -- if rbuf is valid or is set

                                                --   valid this cycle (use n.!!)

          n.rdone := '1';                         -- set DONE

          if r.rie = '1' then                     -- if rx interrupt enabled

            n.rintreq := '1';                       -- request interrupt 

          end if;

        end if;

      end if;

    end if;

    if EI_ACK_RX = '1' then

      n.rintreq := '0';

    end if;

    if EI_ACK_TX = '1' then

      n.xintreq := '0';

    end if;

    N_REGS <= n;

    IB_SRES.dout <= idout;

    IB_SRES.ack  <= ibsel;

    IB_SRES.busy <= '0';

    RRI_LAM <= ilam;

    EI_REQ_RX <= r.rintreq;

    EI_REQ_TX <= r.xintreq;

  end process proc_next;

end syn;