fx2_3fifoctl_ic.vhd

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-- $Id: fx2_3fifoctl_ic.vhd 1181 2019-07-08 17:00:50Z mueller $
-- SPDX-License-Identifier: GPL-3.0-or-later
-- Copyright 2012-2017 by Walter F.J. Mueller <W.F.J.Mueller@gsi.de>
-- 
------------------------------------------------------------------------------
-- Module Name:    fx2_3fifoctl_ic - syn
-- Description:    Cypress EZ-USB FX2 controller (3 fifo; int clk)
--
-- Dependencies:   vlib/xlib/iob_reg_o
--                 vlib/xlib/iob_reg_i_gen
--                 vlib/xlib/iob_reg_o_gen
--                 vlib/xlib/iob_reg_io_gen
--                 memlib/fifo_2c_dram
--
-- Test bench:     -
-- Target Devices: generic
-- Tool versions:  xst 13.3-14.7; ghdl 0.29-0.34
--
-- Synthesized (xst):
-- Date         Rev  ise         Target      flop lutl lutm slic t peri
-- 2017-04-30   888  14.7 131013 xc6slx16-2   207  207   48  125 s  6.9/5.8
-- 2012-01-15   453  13.3   O76x xc3s1200e-4  157  265   96  243 s  7.7/7.4
-- 2012-01-15   453  13.3   O76x xc3s1200e-4  156  259   96  238 s  7.9/7.5
--
-- Revision History: 
-- Date         Rev Version  Comment
-- 2017-04-30   888   1.2    BUGFIX: resolve rx fifo threshold deadlock
--                           add fsm_* monitor lines
-- 2013-01-04   469   1.1    BUGFIX: redo rx logic, now properly pipelined
-- 2012-01-09   453   1.0    Initial version (derived from 2fifo_ic)
--
------------------------------------------------------------------------------
 
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
 
use work.slvtypes.all;
use work.xlib.all;
use work.memlib.all;
use work.fx2lib.all;
 
entity fx2_3fifoctl_ic is               -- EZ-USB FX2 controller(3 fifo; int clk)
  generic (
    RXFAWIDTH : positive :=  5;         -- receive  fifo address width
    TXFAWIDTH : positive :=  5;         -- transmit fifo address width
    PETOWIDTH : positive :=  7;         -- packet end time-out counter width
    CCWIDTH :   positive :=  5;         -- chunk counter width
    RXAEMPTY_THRES : natural := 1;      -- threshold for rx aempty flag
    TXAFULL_THRES  : natural := 1;      -- threshold for tx afull flag
    TX2AFULL_THRES : natural := 1);     -- threshold for tx2 afull flag
  port (
    CLK : in slbit;                     -- clock
    RESET : in slbit := '0';            -- reset
    RXDATA : out slv8;                  -- receive data out
    RXVAL : out slbit;                  -- receive data valid
    RXHOLD : in slbit;                  -- receive data hold
    RXAEMPTY : out slbit;               -- receive almost empty flag
    TXDATA : in slv8;                   -- transmit 1 data in
    TXENA : in slbit;                   -- transmit 1 data enable
    TXBUSY : out slbit;                 -- transmit 1 data busy
    TXAFULL : out slbit;                -- transmit 1 almost full flag
    TX2DATA : in slv8;                  -- transmit 2 data in
    TX2ENA : in slbit;                  -- transmit 2 data enable
    TX2BUSY : out slbit;                -- transmit 2 data busy
    TX2AFULL : out slbit;               -- transmit 2 almost full flag
    MONI : out fx2ctl_moni_type;        -- monitor port data
    I_FX2_IFCLK : in slbit;             -- fx2: interface clock
    O_FX2_FIFO : out slv2;              -- fx2: fifo address
    I_FX2_FLAG : in slv4;               -- fx2: fifo flags
    O_FX2_SLRD_N : out slbit;           -- fx2: read enable    (act.low)
    O_FX2_SLWR_N : out slbit;           -- fx2: write enable   (act.low)
    O_FX2_SLOE_N : out slbit;           -- fx2: output enable  (act.low)
    O_FX2_PKTEND_N : out slbit;         -- fx2: packet end     (act.low)
    IO_FX2_DATA : inout slv8            -- fx2: data lines
  );
end fx2_3fifoctl_ic;
 
 
architecture syn of fx2_3fifoctl_ic is
 
  constant c_rxfifo : slv2 := c_fifo_ep4;
  constant c_txfifo : slv2 := c_fifo_ep6;
  constant c_tx2fifo: slv2 := c_fifo_ep8;
 
  constant c_flag_prog   : integer := 0;
  constant c_flag_tx_ff  : integer := 1;
  constant c_flag_rx_ef  : integer := 2;
  constant c_flag_tx2_ff : integer := 3;
  
  type state_type is (
    s_idle,                             -- s_idle: idle state
    s_rxprep0,                          -- s_rxprep0: switch to rx-fifo
    s_rxprep1,                          -- s_rxprep1: fifo addr setup
    s_rxprep2,                          -- s_rxprep2: wait for flags
    s_rxdisp,                           -- s_rxdisp: read, dispatch
    s_rxpipe,                           -- s_rxpipe: read, pipe wait
    s_txprep0,                          -- s_txprep0: switch to tx-fifo
    s_txprep1,                          -- s_txprep1: fifo addr setup
    s_txprep2,                          -- s_txprep2: wait for flags
    s_txdisp,                           -- s_txdisp: write, dispatch
    s_tx2prep0,                         -- s_tx2prep0: switch to tx2-fifo
    s_tx2prep1,                         -- s_tx2prep1: fifo addr setup
    s_tx2prep2,                         -- s_tx2prep2: wait for flags
    s_tx2disp                           -- s_tx2disp: write, dispatch
  );
  
  type regs_type is record
    state : state_type;                 -- state
    petocnt : slv(PETOWIDTH-1 downto 0);  -- pktend 1 time out counter
    pe2tocnt : slv(PETOWIDTH-1 downto 0); -- pktend 2 time out counter
    pepend : slbit;                     -- pktend 1 pending
    pe2pend : slbit;                    -- pktend 2 pending
    rxpipe1 : slbit;                    -- read pipe 1: iob capture stage
    rxpipe2 : slbit;                    -- read pipe 2: fifo write stage
    ccnt : slv(CCWIDTH-1 downto 0);     -- chunk counter
    moni_ep4_sel : slbit;               -- ep4 (rx) select
    moni_ep6_sel : slbit;               -- ep6 (tx) select
    moni_ep8_sel : slbit;               -- ep8 (tx2) select
    moni_ep4_pf : slbit;                -- ep4 (rx) prog flag
    moni_ep6_pf : slbit;                -- ep6 (tx) prog flag
    moni_ep8_pf : slbit;                -- ep8 (tx2) prog flag
  end record regs_type;
 
  constant petocnt_init : slv(PETOWIDTH-1 downto 0) := (others=>'0');
  constant ccnt_init : slv(CCWIDTH-1 downto 0) := (others=>'0');
 
  constant regs_init : regs_type := (
    s_idle,                             -- state
    petocnt_init,                       -- petocnt
    petocnt_init,                       -- pe2tocnt
    '0','0',                            -- pepend,pe2pend
    '0','0',                            -- rxpipe1, rxpipe2
    ccnt_init,                          -- ccnt
    '0','0','0',                        -- moni_ep(4|6|8)_sel
    '0','0','0'                         -- moni_ep(4|6|8)_pf
  );
    
  constant rxfifo_thres : natural := 3;  -- required free space in rx fifo to
                                         -- start rx pipeline
 
  signal R_REGS : regs_type := regs_init;  -- state registers
  signal N_REGS : regs_type := regs_init;  -- next value state regs
 
  signal FX2_FIFO     : slv2 := (others=>'0');
  signal FX2_FIFO_CE  : slbit := '0';
  signal FX2_FLAG_N   : slv4 := (others=>'0');
  signal FX2_SLRD_N   : slbit := '1';
  signal FX2_SLWR_N   : slbit := '1';
  signal FX2_SLOE_N   : slbit := '1';
  signal FX2_PKTEND_N : slbit := '1';
  signal FX2_DATA_CEI : slbit := '0';
  signal FX2_DATA_CEO : slbit := '0';
  signal FX2_DATA_OE  : slbit := '0';
  signal FX2_DATA_DO  : slv8 := (others=>'0');
 
  signal RXFIFO_DI  : slv8 := (others=>'0');
  signal RXFIFO_ENA  : slbit := '0';
  signal RXFIFO_BUSY : slbit := '0';
  signal RXSIZE_FX2  : slv(RXFAWIDTH-1 downto 0) := (others=>'0');
  signal RXSIZE_USR  : slv(RXFAWIDTH-1 downto 0) := (others=>'0');
  signal TXFIFO_DO   : slv8 := (others=>'0');
  signal TXFIFO_VAL  : slbit := '0';
  signal TXFIFO_HOLD : slbit := '0';
  signal TXSIZE_FX2  : slv(TXFAWIDTH-1 downto 0) := (others=>'0');
  signal TXSIZE_USR  : slv(TXFAWIDTH-1 downto 0) := (others=>'0');
  signal TX2FIFO_DO   : slv8 := (others=>'0');
  signal TX2FIFO_VAL  : slbit := '0';
  signal TX2FIFO_HOLD : slbit := '0';
  signal TX2SIZE_FX2  : slv(TXFAWIDTH-1 downto 0) := (others=>'0');
  signal TX2SIZE_USR  : slv(TXFAWIDTH-1 downto 0) := (others=>'0');
 
  signal TXBUSY_L : slbit := '0';
  signal TX2BUSY_L : slbit := '0';
 
  signal R_MONI_C : fx2ctl_moni_type := fx2ctl_moni_init;
  signal R_MONI_S : fx2ctl_moni_type := fx2ctl_moni_init;
 
begin
 
  assert RXAEMPTY_THRES<=2**RXFAWIDTH-1 and
         TXAFULL_THRES<=2**TXFAWIDTH-1 and
         TX2AFULL_THRES<=2**TXFAWIDTH-1
    report "assert((RXAEMPTY|TXAFULL|TX2AFULL)_THRES <= 2**(RX|TX)FAWIDTH)-1"
    severity failure;
 
 
  IOB_FX2_FIFO : iob_reg_o_gen
    generic map (
      DWIDTH => 2,
      INIT   => '0')
    port map (
      CLK => I_FX2_IFCLK,
      CE  => FX2_FIFO_CE,
      DO  => FX2_FIFO,
      PAD => O_FX2_FIFO
    );
  
  IOB_FX2_FLAG : iob_reg_i_gen
    generic map (
      DWIDTH => 4,
      INIT   => '0')
    port map (
      CLK => I_FX2_IFCLK,
      CE  => '1',
      DI  => FX2_FLAG_N,
      PAD => I_FX2_FLAG
    );
  
  IOB_FX2_SLRD : iob_reg_o
    generic map (
      INIT   => '1')
    port map (
      CLK => I_FX2_IFCLK,
      CE  => '1',
      DO  => FX2_SLRD_N,
      PAD => O_FX2_SLRD_N
    );
  
  IOB_FX2_SLWR : iob_reg_o
    generic map (
      INIT   => '1')
    port map (
      CLK => I_FX2_IFCLK,
      CE  => '1',
      DO  => FX2_SLWR_N,
      PAD => O_FX2_SLWR_N
    );
  
  IOB_FX2_SLOE : iob_reg_o
    generic map (
      INIT   => '1')
    port map (
      CLK => I_FX2_IFCLK,
      CE  => '1',
      DO  => FX2_SLOE_N,
      PAD => O_FX2_SLOE_N
    );
    
  IOB_FX2_PKTEND : iob_reg_o
    generic map (
      INIT   => '1')
    port map (
      CLK => I_FX2_IFCLK,
      CE  => '1',
      DO  => FX2_PKTEND_N,
      PAD => O_FX2_PKTEND_N
    );
 
  IOB_FX2_DATA : iob_reg_io_gen
    generic map (
      DWIDTH => 8,
      PULL   => "KEEP")
    port map (
      CLK => I_FX2_IFCLK,
      CEI => FX2_DATA_CEI,
      CEO => FX2_DATA_CEO,
      OE  => FX2_DATA_OE,
      DI  => RXFIFO_DI,                 -- input data   (read from pad)
      DO  => FX2_DATA_DO,               -- output data  (write  to pad)
      PAD => IO_FX2_DATA
    );
 
  RXFIFO : fifo_2c_dram                -- input fifo, 2 clock, dram based
    generic map (
      AWIDTH => RXFAWIDTH,
      DWIDTH => 8)
    port map (
      CLKW   => I_FX2_IFCLK,
      CLKR   => CLK,
      RESETW => '0',
      RESETR => RESET,
      DI     => RXFIFO_DI,
      ENA    => RXFIFO_ENA,
      BUSY   => RXFIFO_BUSY,
      DO     => RXDATA,
      VAL    => RXVAL,
      HOLD   => RXHOLD,
      SIZEW  => RXSIZE_FX2,
      SIZER  => RXSIZE_USR
    );
 
  TXFIFO : fifo_2c_dram                -- output fifo, 2 clock, dram based
    generic map (
      AWIDTH => TXFAWIDTH,
      DWIDTH => 8)
    port map (
      CLKW   => CLK,
      CLKR   => I_FX2_IFCLK,
      RESETW => RESET,
      RESETR => '0',
      DI     => TXDATA,
      ENA    => TXENA,
      BUSY   => TXBUSY_L,
      DO     => TXFIFO_DO,
      VAL    => TXFIFO_VAL,
      HOLD   => TXFIFO_HOLD,
      SIZEW  => TXSIZE_USR,
      SIZER  => TXSIZE_FX2
    );
 
  TX2FIFO : fifo_2c_dram               -- output 2 fifo, 2 clock, dram based
    generic map (
      AWIDTH => TXFAWIDTH,
      DWIDTH => 8)
    port map (
      CLKW   => CLK,
      CLKR   => I_FX2_IFCLK,
      RESETW => RESET,
      RESETR => '0',
      DI     => TX2DATA,
      ENA    => TX2ENA,
      BUSY   => TX2BUSY_L,
      DO     => TX2FIFO_DO,
      VAL    => TX2FIFO_VAL,
      HOLD   => TX2FIFO_HOLD,
      SIZEW  => TX2SIZE_USR,
      SIZER  => TX2SIZE_FX2
    );
 
  proc_regs: process (I_FX2_IFCLK)
  begin
 
    if rising_edge(I_FX2_IFCLK) then
      if RESET = '1' then
        R_REGS <= regs_init;
      else
        R_REGS <= N_REGS;
      end if;
    end if;
 
  end process proc_regs;
 
  proc_next: process (R_REGS, FX2_FLAG_N, TXFIFO_VAL, TX2FIFO_VAL,
                      TXFIFO_DO, TX2FIFO_DO, RXSIZE_FX2, TXBUSY_L, TX2BUSY_L)
 
    variable r : regs_type := regs_init;
    variable n : regs_type := regs_init;
 
    variable ififo_ce : slbit := '0';
    variable ififo    : slv2 := "00";
 
    variable irxfifo_ena   : slbit := '0';
    variable itxfifo_hold  : slbit := '0';
    variable itx2fifo_hold : slbit := '0';
 
    variable islrd   : slbit := '0';
    variable islwr   : slbit := '0';
    variable isloe   : slbit := '0';
    variable ipktend : slbit := '0';
 
    variable idata_cei : slbit := '0';
    variable idata_ceo : slbit := '0';
    variable idata_oe  : slbit := '0';
    variable idata_do  : slv8 := (others=>'0');
 
    variable slrxok  : slbit := '0';
    variable sltxok  : slbit := '0';
    variable sltx2ok : slbit := '0';
    variable pipeok  : slbit := '0';
    variable rxfifook : slbit := '0';
 
    variable cc_clr : slbit := '0';
    variable cc_cnt : slbit := '0';
    variable cc_done : slbit := '0';
         
  begin
 
    r := R_REGS;
    n := R_REGS;
 
    ififo_ce := '0';
    ififo    := "00";
 
    irxfifo_ena   := '0';
    itxfifo_hold  := '1';
    itx2fifo_hold := '1';
  
    islrd   := '0';
    islwr   := '0';
    isloe   := '0';
    ipktend := '0';
 
    idata_cei := '0';
    idata_ceo := '0';
    idata_oe  := '0';
    idata_do  := TXFIFO_DO;
 
    slrxok  := FX2_FLAG_N(c_flag_rx_ef);  -- empty flag is act.low!
    sltxok  := FX2_FLAG_N(c_flag_tx_ff);  --  full flag is act.low!
    sltx2ok := FX2_FLAG_N(c_flag_tx2_ff); --  full flag is act.low!
    pipeok  := FX2_FLAG_N(c_flag_prog);   -- almost flag is act.low!
 
    rxfifook := '0';
    if unsigned(RXSIZE_FX2)>rxfifo_thres then -- enough space in rx fifo ?
      rxfifook := '1';
    end if;
 
    cc_clr := '0';
    cc_cnt := '0';
    if unsigned(r.ccnt) = 0  then
      cc_done := '1';
    else
      cc_done := '0';
    end if;
    
    n.rxpipe1  := '0';
 
    case r.state is
      when s_idle =>                    -- s_idle:
        if slrxok='1' and rxfifook='1' then -- rx data and space in fifo
          ififo_ce := '1';
          ififo    := c_rxfifo;
          n.state := s_rxprep1;
        elsif sltxok='1' and (TXFIFO_VAL='1' or r.pepend='1')then
          ififo_ce := '1';
          ififo    := c_txfifo;
          n.state := s_txprep1;          
        elsif sltx2ok='1' and (TX2FIFO_VAL='1' or r.pe2pend='1')then
          ififo_ce := '1';
          ififo    := c_tx2fifo;
          n.state := s_tx2prep1;          
        end if;
 
      when s_rxprep0 =>                 -- s_rxprep0: switch to rx-fifo
        ififo_ce := '1';
        ififo    := c_rxfifo;
        n.state := s_rxprep1;
 
      when s_rxprep1 =>                 -- s_rxprep1: fifo addr setup
        cc_clr  := '1';
        n.state := s_rxprep2;
 
      when s_rxprep2 =>                 -- s_rxprep2: wait for flags
        isloe   := '1';
        n.state := s_rxdisp;
 
      when s_rxdisp =>                  -- s_rxdisp: read, dispatch
        isloe := '1';
        -- if chunk done and tx or pe pending and possible
        if cc_done='1' and sltxok='1' and (TXFIFO_VAL='1' or r.pepend='1') then
          if r.rxpipe1='1' or r.rxpipe2='1' then -- rx pipe busy ?
            n.state := s_rxdisp;            -- wait
          else
            n.state := s_txprep0;           -- otherwise switch to tx flow
          end if;
        -- if chunk done and tx2 or pe2 pending and possible
        elsif cc_done='1' and sltx2ok='1' and (TX2FIFO_VAL='1' or r.pe2pend='1')
        then
          if r.rxpipe1='1' or r.rxpipe2='1' then -- rx pipe busy ?
            n.state := s_rxdisp;            -- wait
          else
            n.state := s_tx2prep0;
          end if;
        -- if more rx to do and possible
        elsif slrxok='1' and rxfifook='1' then
          islrd := '1';
          cc_cnt := '1';
          n.rxpipe1 := '1';
          if pipeok='1' then
            n.state := s_rxdisp;             -- 1 cycle read
            --n.state := s_rxprep2;            -- 2 cycle read
          else
            n.state := s_rxpipe;
          end if;
        -- otherwise back to idle
        else
          if r.rxpipe1='1' or r.rxpipe2='1' then -- rx pipe busy ?
            n.state := s_rxdisp;            -- wait
          else
            n.state := s_idle;              -- to idle
          end if;
        end if;
 
      when s_rxpipe =>                  -- s_rxpipe:  read, pipe wait
        isloe := '1';
        n.state := s_rxprep2;
 
      when s_txprep0 =>                 -- s_txprep0: switch to tx-fifo
        ififo_ce := '1';
        ififo    := c_txfifo;
        n.state := s_txprep1;
 
      when s_txprep1 =>                 -- s_txprep1: fifo addr setup
        cc_clr  := '1';
        n.state := s_txprep2;
 
      when s_txprep2 =>                 -- s_txprep2: wait for flags
        n.state := s_txdisp;
 
      when s_txdisp =>                  -- s_txdisp: write, dispatch
        -- if chunk done and tx2 or pe2 pending and possible
        if cc_done='1' and sltx2ok='1' and (TX2FIFO_VAL='1' or r.pe2pend='1')
        then
          n.state := s_tx2prep0;
        -- if chunk done and rx pending and possible
        elsif cc_done='1' and slrxok='1' and rxfifook='1' then
          n.state := s_rxprep0;
        -- if pktend to do and possible
        elsif sltxok = '1' and r.pepend = '1' then
          ipktend  := '1';
          n.pepend := '0';
          n.state := s_idle;
        -- if more tx to do and possible
        elsif sltxok = '1' and TXFIFO_VAL = '1' then
          cc_cnt := '1';                  -- inc chunk count
          n.pepend := '0';                -- cancel pe (avoid back-2-back tx+pe)
          itxfifo_hold := '0';
          idata_do  := TXFIFO_DO;
          idata_ceo := '1';
          idata_oe  := '1';
          islwr     := '1';
          if pipeok = '1' then           -- if not almost full
            n.state   := s_txdisp;          -- stream 
          else
            n.state   := s_txprep1;         -- wait for full flag
          end if;
        -- otherwise back to idle
        else
          n.state := s_idle;
        end if;
        
      when s_tx2prep0 =>                -- s_tx2prep0: switch to tx2-fifo
        ififo_ce := '1';
        ififo    := c_tx2fifo;
        n.state := s_tx2prep1;
 
      when s_tx2prep1 =>                -- s_tx2prep1: fifo addr setup
        cc_clr  := '1';
        n.state := s_tx2prep2;
 
      when s_tx2prep2 =>                -- s_tx2prep2: wait for flags
        n.state := s_tx2disp;
 
      when s_tx2disp =>                 -- s_tx2disp: write, dispatch
        -- if chunk done and rx pending and possible
        if cc_done='1' and slrxok='1' and rxfifook='1' then
          n.state := s_rxprep0;
        -- if chunk done and tx or pe pending and possible
        elsif cc_done='1' and sltxok='1' and (TXFIFO_VAL='1' or r.pepend='1')
        then
          n.state := s_txprep0;
        -- if pktend 2 to do and possible
        elsif sltx2ok = '1' and r.pe2pend = '1' then
          ipktend  := '1';
          n.pe2pend := '0';
          n.state := s_idle;
        -- if more tx2 to do and possible
        elsif sltx2ok = '1' and TX2FIFO_VAL = '1' then
          cc_cnt := '1';                  -- inc chunk count
          n.pe2pend := '0';               -- cancel pe (avoid back-2-back tx+pe)
          itx2fifo_hold := '0';
          idata_do  := TX2FIFO_DO;
          idata_ceo := '1';
          idata_oe  := '1';
          islwr     := '1';
          if pipeok = '1' then           -- if not almost full
            n.state   := s_tx2disp;        -- stream 
          else
            n.state   := s_tx2prep1;       -- wait for full flag
          end if;
        -- otherwise back to idle
        else
          n.state := s_idle;
        end if;
        
      when others => null;
    end case;
 
    -- rx pipe handling
    idata_cei   := r.rxpipe1;
    n.rxpipe2   := r.rxpipe1;
    irxfifo_ena := r.rxpipe2;
    
    -- chunk counter handling
    if cc_clr = '1' then
      n.ccnt := (others=>'1');
    elsif cc_cnt='1' and unsigned(r.ccnt) > 0 then
      n.ccnt := slv(unsigned(r.ccnt) - 1);
    end if;
    
    -- pktend time-out handling:
    --   if tx fifo is non-empty, set counter to max
    --   if tx fifo is empty, count down every ifclk cycle
    --   on 1->0 transition queue pktend request
    if TXFIFO_VAL = '1' then
      n.petocnt := (others=>'1');
    else
      if unsigned(r.petocnt) /= 0 then
        n.petocnt := slv(unsigned(r.petocnt) - 1);
        if unsigned(r.petocnt) = 1 then
          n.pepend := '1';
        end if;
      end if;
    end if;
    if TX2FIFO_VAL = '1' then
      n.pe2tocnt := (others=>'1');
    else
      if unsigned(r.pe2tocnt) /= 0 then
        n.pe2tocnt := slv(unsigned(r.pe2tocnt) - 1);
        if unsigned(r.pe2tocnt) = 1 then
          n.pe2pend := '1';
        end if;
      end if;
    end if;
 
    n.moni_ep4_sel := '0';
    n.moni_ep6_sel := '0';
    n.moni_ep8_sel := '0';
    if r.state = s_rxdisp or r.state = s_rxpipe then
      n.moni_ep4_sel := '1';
      n.moni_ep4_pf  := not FX2_FLAG_N(c_flag_prog);
    elsif r.state = s_txdisp then
      n.moni_ep6_sel := '1';
      n.moni_ep6_pf  := not FX2_FLAG_N(c_flag_prog);
    elsif r.state = s_tx2disp then
      n.moni_ep8_sel := '1';
      n.moni_ep8_pf  := not FX2_FLAG_N(c_flag_prog);
    end if;
 
    N_REGS <= n;
 
    FX2_FIFO_CE  <= ififo_ce;
    FX2_FIFO     <= ififo;
 
    FX2_SLRD_N   <= not islrd;
    FX2_SLWR_N   <= not islwr;
    FX2_SLOE_N   <= not isloe;
    FX2_PKTEND_N <= not ipktend;
 
    FX2_DATA_CEI <= idata_cei;
    FX2_DATA_CEO <= idata_ceo;
    FX2_DATA_OE  <= idata_oe;
    FX2_DATA_DO  <= idata_do;
 
    RXFIFO_ENA   <= irxfifo_ena;
    TXFIFO_HOLD  <= itxfifo_hold;
    TX2FIFO_HOLD <= itx2fifo_hold;
    
  end process proc_next;
 
  proc_moni: process (CLK)
  begin
 
    if rising_edge(CLK) then
      if RESET = '1' then
        R_MONI_C <= fx2ctl_moni_init;
        R_MONI_S <= fx2ctl_moni_init;
      else
        R_MONI_C <= fx2ctl_moni_init;
        R_MONI_C.fifo_ep4        <= R_REGS.moni_ep4_sel;
        R_MONI_C.fifo_ep6        <= R_REGS.moni_ep6_sel;
        R_MONI_C.fifo_ep8        <= R_REGS.moni_ep8_sel;
        R_MONI_C.flag_ep4_empty  <= not FX2_FLAG_N(c_flag_rx_ef);
        R_MONI_C.flag_ep4_almost <= R_REGS.moni_ep4_pf;
        R_MONI_C.flag_ep6_full   <= not FX2_FLAG_N(c_flag_tx_ff);
        R_MONI_C.flag_ep6_almost <= R_REGS.moni_ep6_pf;
        R_MONI_C.flag_ep8_full   <= not FX2_FLAG_N(c_flag_tx2_ff);
        R_MONI_C.flag_ep8_almost <= R_REGS.moni_ep8_pf;
        R_MONI_C.slrd            <= not FX2_SLRD_N;
        R_MONI_C.slwr            <= not FX2_SLWR_N;
        R_MONI_C.pktend          <= not FX2_PKTEND_N;
        case R_REGS.state is
          when s_idle     => R_MONI_C.fsm_idle <= '1';
          when s_rxprep0  => R_MONI_C.fsm_prep <= '1'; R_MONI_C.fsm_rx  <= '1';
          when s_rxprep1  => R_MONI_C.fsm_prep <= '1'; R_MONI_C.fsm_rx  <= '1';
          when s_rxprep2  => R_MONI_C.fsm_prep <= '1'; R_MONI_C.fsm_rx  <= '1';
          when s_rxdisp   => R_MONI_C.fsm_disp <= '1'; R_MONI_C.fsm_rx  <= '1';
          when s_rxpipe   => R_MONI_C.fsm_pipe <= '1'; R_MONI_C.fsm_rx  <= '1';
          when s_txprep0  => R_MONI_C.fsm_prep <= '1'; R_MONI_C.fsm_tx  <= '1'; 
          when s_txprep1  => R_MONI_C.fsm_prep <= '1'; R_MONI_C.fsm_tx  <= '1';
          when s_txprep2  => R_MONI_C.fsm_prep <= '1'; R_MONI_C.fsm_tx  <= '1';
          when s_txdisp   => R_MONI_C.fsm_disp <= '1'; R_MONI_C.fsm_tx  <= '1';
          when s_tx2prep0 => R_MONI_C.fsm_prep <= '1'; R_MONI_C.fsm_tx2 <= '1'; 
          when s_tx2prep1 => R_MONI_C.fsm_prep <= '1'; R_MONI_C.fsm_tx2 <= '1';
          when s_tx2prep2 => R_MONI_C.fsm_prep <= '1'; R_MONI_C.fsm_tx2 <= '1';
          when s_tx2disp  => R_MONI_C.fsm_disp <= '1'; R_MONI_C.fsm_tx2 <= '1';
          when others => null;
        end case;
 
        R_MONI_S <= R_MONI_C;
      end if;
    end if;
 
  end process proc_moni;
 
  proc_almost: process (RXSIZE_USR, TXSIZE_USR, TX2SIZE_USR)
  begin
 
    -- rxsize_usr is the number of bytes to read
    -- txsize_usr is the number of bytes to write
    
    if unsigned(RXSIZE_USR) <= RXAEMPTY_THRES then
      RXAEMPTY <= '1';
    else
      RXAEMPTY <= '0';
    end if;
 
    if unsigned(TXSIZE_USR) <= TXAFULL_THRES then
      TXAFULL <= '1';
    else
      TXAFULL <= '0';
    end if;
 
    if unsigned(TX2SIZE_USR) <= TX2AFULL_THRES then
      TX2AFULL <= '1';
    else
      TX2AFULL <= '0';
    end if;
 
  end process proc_almost;
 
  TXBUSY  <= TXBUSY_L;
  TX2BUSY <= TX2BUSY_L;
 
  MONI <= R_MONI_S;
  
end syn;