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-- $Id: serport_1clock.vhd 476 2013-01-26 22:23:53Z mueller $

--

-- Copyright 2011- 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:    serport_1clock - syn

-- Description:    serial port: serial port module, 1 clock domain

--

-- Dependencies:   serport_uart_rxtx_ab

--                 serport_xonrx

--                 serport_xontx

--                 memlib/fifo_1c_dram

-- Test bench:     -

-- Target Devices: generic

-- Tool versions:  xst 13.1; ghdl 0.29

--

-- Synthesized (xst):

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

-- 2011-11-13   424 13.1    O40d xc3s1000-4   157  337   64  232 s  9.9

--

-- Revision History: 

-- Date         Rev Version  Comment

-- 2011-12-10   438   1.0.2  internal reset on abact

-- 2011-12-09   437   1.0.1  rename stat->moni port

-- 2011-11-13   424   1.0    Initial version

-- 2011-10-23   419   0.5    First draft

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

library ieee;

use ieee.std_logic_1164.all;

use ieee.numeric_std.all;

use work.slvtypes.all;

use work.serportlib.all;

use work.memlib.all;

entity serport_1clock is                -- serial port module, 1 clock domain

  generic (

    CDWIDTH : positive := 13;           -- clk divider width

    CDINIT : natural   := 15;           -- clk divider initial/reset setting

    RXFAWIDTH : natural :=  5;          -- rx fifo address width

    TXFAWIDTH : natural :=  5);         -- tx fifo address width

  port (

    CLK : in slbit;                     -- clock

    CE_MSEC : in slbit;                 -- 1 msec clock enable

    RESET : in slbit;                   -- reset

    ENAXON : in slbit;                  -- enable xon/xoff handling

    ENAESC : in slbit;                  -- enable xon/xoff escaping

    RXDATA : out slv8;                  -- receiver data out

    RXVAL : out slbit;                  -- receiver data valid

    RXHOLD : in slbit;                  -- receiver data hold

    TXDATA : in slv8;                   -- transmit data in

    TXENA : in slbit;                   -- transmit data enable

    TXBUSY : out slbit;                 -- transmit busy

    MONI : out serport_moni_type;       -- serport monitor port

    RXSD : in slbit;                    -- receive serial data (uart view)

    TXSD : out slbit;                   -- transmit serial data (uart view)

    RXRTS_N : out slbit;                -- receive rts (uart view, act.low)

    TXCTS_N : in slbit                  -- transmit cts (uart view, act.low)

  );

end serport_1clock;

architecture syn of serport_1clock is

  signal R_RXOK : slbit := '1';

  signal RESET_INT : slbit := '0';

  signal UART_RXDATA : slv8 := (others=>'0');

  signal UART_RXVAL : slbit := '0';

  signal UART_TXDATA : slv8 := (others=>'0');

  signal UART_TXENA : slbit := '0';

  signal UART_TXBUSY : slbit := '0';

  signal XONTX_TXENA : slbit := '0';

  signal XONTX_TXBUSY : slbit := '0';

  signal RXFIFO_DI : slv8 := (others=>'0');

  signal RXFIFO_ENA : slbit := '0';

  signal RXFIFO_BUSY : slbit := '0';

  signal RXFIFO_SIZE : slv(RXFAWIDTH downto 0) := (others=>'0');

  signal TXFIFO_DO : slv8 := (others=>'0');

  signal TXFIFO_VAL : slbit := '0';

  signal TXFIFO_HOLD : slbit := '0';

  signal RXERR  : slbit := '0';

  signal RXOVR  : slbit := '0';

  signal RXACT  : slbit := '0';

  signal ABACT  : slbit := '0';

  signal ABDONE : slbit := '0';

  signal ABCLKDIV : slv(CDWIDTH-1 downto 0) := (others=>'0');

  signal TXOK : slbit := '0';

  signal RXOK : slbit := '0';

begin

  assert CDWIDTH<=16

    report "assert(CDWIDTH<=16): max width of UART clock divider"

    severity failure;

  UART : serport_uart_rxtx_ab           -- uart, rx+tx+autobauder combo

  generic map (

    CDWIDTH => CDWIDTH,

    CDINIT  => CDINIT)

  port map (

    CLK      => CLK,

    CE_MSEC  => CE_MSEC,

    RESET    => RESET,

    RXSD     => RXSD,

    RXDATA   => UART_RXDATA,

    RXVAL    => UART_RXVAL,

    RXERR    => RXERR,

    RXACT    => RXACT,

    TXSD     => TXSD,

    TXDATA   => UART_TXDATA,

    TXENA    => UART_TXENA,

    TXBUSY   => UART_TXBUSY,

    ABACT    => ABACT,

    ABDONE   => ABDONE,

    ABCLKDIV => ABCLKDIV

  );

  RESET_INT <= RESET or ABACT;

  XONRX : serport_xonrx                 --  xon/xoff logic rx path

  port map (

    CLK         => CLK,

    RESET       => RESET_INT,

    ENAXON      => ENAXON,

    ENAESC      => ENAESC,

    UART_RXDATA => UART_RXDATA,

    UART_RXVAL  => UART_RXVAL,

    RXDATA      => RXFIFO_DI,

    RXVAL       => RXFIFO_ENA,

    RXHOLD      => RXFIFO_BUSY,

    RXOVR       => RXOVR,

    TXOK        => TXOK

  );

  XONTX : serport_xontx                 --  xon/xoff logic tx path

  port map (

    CLK         => CLK,

    RESET       => RESET_INT,

    ENAXON      => ENAXON,

    ENAESC      => ENAESC,

    UART_TXDATA => UART_TXDATA,

    UART_TXENA  => XONTX_TXENA,

    UART_TXBUSY => XONTX_TXBUSY,

    TXDATA      => TXFIFO_DO,

    TXENA       => TXFIFO_VAL,

    TXBUSY      => TXFIFO_HOLD,

    RXOK        => RXOK,

    TXOK        => TXOK

  );

  RXFIFO : fifo_1c_dram                 -- input fifo, 1 clock, dram based

  generic map (

    AWIDTH => RXFAWIDTH,

    DWIDTH => 8)

  port map (

    CLK   => CLK,

    RESET => RESET_INT,

    DI    => RXFIFO_DI,

    ENA   => RXFIFO_ENA,

    BUSY  => RXFIFO_BUSY,

    DO    => RXDATA,

    VAL   => RXVAL,

    HOLD  => RXHOLD,

    SIZE  => RXFIFO_SIZE

  );

  TXFIFO : fifo_1c_dram                 -- input fifo, 1 clock, dram based

  generic map (

    AWIDTH => TXFAWIDTH,

    DWIDTH => 8)

  port map (

    CLK   => CLK,

    RESET => RESET_INT,

    DI    => TXDATA,

    ENA   => TXENA,

    BUSY  => TXBUSY,

    DO    => TXFIFO_DO,

    VAL   => TXFIFO_VAL,

    HOLD  => TXFIFO_HOLD,

    SIZE  => open

  );

  -- receive back preasure

  --    on if fifo more than 3/4 full

  --   off if fifo less than 1/2 full

  proc_rxok: process (CLK)

    constant rxsize_rxok_off : slv3 := "011";

    constant rxsize_rxok_on  : slv3 := "010";

    variable rxsize_msb : slv3 := "000";

  begin

    if rising_edge(CLK) then

      if RESET_INT = '1' then

        R_RXOK <= '1';

      else

        rxsize_msb := RXFIFO_SIZE(RXFAWIDTH downto RXFAWIDTH-2);

        if unsigned(rxsize_msb) >=  unsigned(rxsize_rxok_off) then

          R_RXOK <= '0';

        elsif unsigned(rxsize_msb) <=  unsigned(rxsize_rxok_on) then

          R_RXOK <= '1';

        end if;

      end if;

    end if;

  end process proc_rxok;

  RXOK    <= R_RXOK;

  RXRTS_N <= not R_RXOK;

  proc_cts: process (TXCTS_N, XONTX_TXENA, UART_TXBUSY)

  begin

    if TXCTS_N = '0' then               -- transmit cts asserted

      UART_TXENA   <= XONTX_TXENA;

      XONTX_TXBUSY <= UART_TXBUSY;

    else                                -- transmit cts not asserted

      UART_TXENA   <= '0';

      XONTX_TXBUSY <= '1';

    end if;

  end process proc_cts;

  MONI.rxerr  <= RXERR;

  MONI.rxovr  <= RXOVR;

  MONI.rxact  <= RXACT;

  MONI.txact  <= UART_TXBUSY;

  MONI.abact  <= ABACT;

  MONI.abdone <= ABDONE;

  MONI.rxok   <= RXOK;

  MONI.txok   <= TXOK;

  proc_abclkdiv: process (ABCLKDIV)

  begin

    MONI.abclkdiv <= (others=>'0');

    MONI.abclkdiv(ABCLKDIV'range) <= ABCLKDIV;

  end process proc_abclkdiv;

end syn;