Subversion Repositories open8_urisc

-- Copyright (c)2020 Jeremy Seth Henry
-- All rights reserved.
--
-- Redistribution and use in source and binary forms, with or without
-- modification, are permitted provided that the following conditions are met:
--     * Redistributions of source code must retain the above copyright
--       notice, this list of conditions and the following disclaimer.
--     * Redistributions in binary form must reproduce the above copyright
--       notice, this list of conditions and the following disclaimer in the
--       documentation and/or other materials provided with the distribution,
--       where applicable (as part of a user interface, debugging port, etc.)
--
-- THIS SOFTWARE IS PROVIDED BY JEREMY SETH HENRY ``AS IS'' AND ANY
-- EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
-- WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
-- DISCLAIMED. IN NO EVENT SHALL JEREMY SETH HENRY BE LIABLE FOR ANY
-- DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
-- (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
-- LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
-- ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-- (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
-- THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
--
-- VHDL Units :  o8_sdlc_if
-- Description:  Provides a full memory-mapped SDLC stack with automatic CRC16
--                Checksum insertion and integrity checking.
--
-- Transmit Memory Map
-- "0_0000_0000" (0x000) TX Buffer START
-- "0_1111_1101" (0x0FD) TX Buffer END
-- "0_1111_1110" (0x0FE) Clock Status*
-- "0_1111_1111" (0x0FF) TX Length / Status**
--
-- Receive Memory Map
-- "1_0000_0000" (0x100) RX Buffer START
-- "1_1111_1110" (0x1FE) RX Buffer END
-- "1_1111_1111" (0x1FF) RX Length / Status
--
-- * Address 0xFE reports the SDLC bit clock status and updates on changes. If
--    the bit clock goes away (BClk_Okay = '0'), the field will report 0x00.
--    otherwise it will report 0xFF. Note that the CPU can overwrite this
--    location, at which point the status will be invalid.
--
-- ** This location serves as the control/status register for the interface
--    1) Writing 0x00 will reset the clock status flag in 0xFE without
--        triggering an interrupt.
--    2) Writing a value between 1 and 253 will trigger the transmit engine,
--        using the write value as the packet length.
--    3) Writing 0xFE or 0xFF will be ignored by the engine.
--    4) This value will change from the user written value to 0xFF once the
--        packet is transmitted.
--
 
library ieee;
  use ieee.std_logic_1164.all;
  use ieee.std_logic_unsigned.all;
  use ieee.std_logic_arith.all;
 
library work;
  use work.open8_pkg.all;
 
library work;
  use work.sdlc_serial_pkg.all;
 
entity o8_sdlc_if is
generic(
  Poly_Init                  : std_logic_vector(15 downto 0) := x"0000";
  Set_As_Master              : boolean := true;
  Clock_Offset               : integer := 6;
  BitClock_Freq              : real := 500000.0;
  Sys_Freq                   : real := 100000000.0;
  Reset_Level                : std_logic := '1';
  Address                    : ADDRESS_TYPE
);
port(
  Clock                      : in  std_logic;
  Reset                      : in  std_logic;
  --
  Bus_Address                : in  ADDRESS_TYPE;
  Wr_Enable                  : in  std_logic;
  Wr_Data                    : in  DATA_TYPE;
  Rd_Enable                  : in  std_logic;
  Rd_Data                    : out DATA_TYPE;
  Interrupt                  : out std_logic;
  -- Serial IO
  SDLC_In                    : in  std_logic;
  SDLC_SClk                  : in  std_logic;
  SDLC_MClk                  : out std_logic;
  SDLC_Out                   : out std_logic
);
end entity;
 
architecture behave of o8_sdlc_if is
 
  -- Connect the CPU to the dual-port memory
  constant Base_Addr         : std_logic_vector(15 downto 9)
                               := Address(15 downto 9);
 
  alias RAM_Upper_Addr       is Bus_Address(15 downto 9);
  alias RAM_Lower_Addr       is Bus_Address(8 downto 0);
 
  signal RAM_Addr_Match      : std_logic := '0';
  signal RAM_Wr_En           : std_logic := '0';
  signal RAM_Rd_En           : std_logic := '0';
  signal Rd_Data_i           : DATA_TYPE := OPEN8_NULLBUS;
 
  constant Reg_Sub_Addr      : std_logic_vector(8 downto 0) :=
                               conv_std_logic_vector(255,9);
 
  signal Reg_Addr            : std_logic_vector(8 downto 0) := (others => '0');
  signal Reg_Wr_En           : std_logic := '0';
  signal Reg_Updated         : std_logic := '0';
  -- Connect the serial engine to the dual-port memory
  signal DP_Addr             : std_logic_vector(8 downto 0) := (others => '0');
  signal DP_Wr_Data          : DATA_IN_TYPE := x"00";
  signal DP_Wr_En            : std_logic := '0';
  signal DP_Rd_Data          : DATA_IN_TYPE := x"00";
 
  signal BClk_RE             : std_logic := '0';
  signal BClk_FE             : std_logic := '0';
 
  signal TX_Wr_En            : std_logic := '0';
  signal TX_Wr_Flag          : std_logic := '0';
  signal TX_Wr_Data          : DATA_IN_TYPE := x"00";
  signal TX_Req_Next         : std_logic := '0';
 
  signal TX_CRC_Clr          : std_logic := '0';
  signal TX_CRC_En           : std_logic := '0';
  signal TX_CRC_Data         : CRC_OUT_TYPE := x"0000";
  alias  TX_CRC_Data_LB      is TX_CRC_Data(7 downto 0);
  alias  TX_CRC_Data_UB      is TX_CRC_Data(15 downto 8);
  signal TX_CRC_Valid        : std_logic := '0';
 
  signal RX_Valid            : std_logic := '0';
  signal RX_Flag             : std_logic := '0';
  signal RX_Data             : DATA_IN_TYPE := x"00";
  signal RX_Idle             : std_logic := '0';
 
  signal RX_CRC_Clr          : std_logic := '0';
  signal RX_CRC_En           : std_logic := '0';
  signal RX_CRC_Data         : CRC_OUT_TYPE := x"0000";
  signal RX_CRC_Valid        : std_logic := '0';
 
  signal BClk_Okay           : std_logic := '0';
 
begin
 
  -- This decode needs to happen immediately, to give the RAM a chance to
  --  do the lookup before we have to set Rd_Data
  RAM_Addr_Match             <= '1' when Base_Addr = RAM_Upper_Addr else '0';
  RAM_Wr_En                  <= RAM_Addr_Match and Wr_Enable;
 
  CPU_RAM_proc: process( Reset, Clock )
  begin
    if( Reset = Reset_Level )then
      Reg_Addr               <= (others => '0');
      Reg_Wr_En              <= '0';
      Reg_Updated            <= '0';
      RAM_Rd_En              <= '0';
      Rd_Data                <= OPEN8_NULLBUS;
    elsif( rising_edge(Clock) )then
      Reg_Addr               <= RAM_Lower_Addr;
      Reg_Wr_En              <= RAM_Addr_Match and Wr_Enable;
 
      Reg_Updated            <= '0';
      if( Reg_Addr = Reg_Sub_Addr )then
        Reg_Updated          <= Reg_Wr_En;
      end if;
 
      RAM_Rd_En              <= RAM_Addr_Match and Rd_Enable;
      Rd_Data                <= OPEN8_NULLBUS;
      if( RAM_Rd_En = '1' )then
        Rd_Data              <= Rd_Data_i;
      end if;
    end if;
  end process;
 
  U_RAM : entity work.ram_dp512b_core
  port map(
    clock                    => Clock,
    address_a                => RAM_Lower_Addr,
    address_b                => DP_Addr,
    data_a                   => Wr_Data,
    data_b                   => DP_Wr_Data,
    wren_a                   => RAM_Wr_En,
    wren_b                   => DP_Wr_En,
    q_a                      => Rd_Data_i,
    q_b                      => DP_Rd_Data
  );
 
  U_BCLK : entity work.sdlc_serial_clk
  generic map(
    Set_As_Master            => Set_As_Master,
    BitClock_Freq            => BitClock_Freq,
    Reset_Level              => Reset_Level,
    Sys_Freq                 => Sys_Freq
  )
  port map(
    Clock                    => Clock,
    Reset                    => Reset,
    --
    BClk_In                  => SDLC_SClk,
    BClk_Out                 => SDLC_MClk,
    BClk_FE                  => BClk_FE,
    BClk_RE                  => BClk_RE,
    BClk_Okay                => BClk_Okay
  );
 
  U_CTRL : entity work.sdlc_serial_ctrl
  generic map(
    Reset_Level              => Reset_Level
  )
  port map(
    Clock                    => Clock,
    Reset                    => Reset,
    --
    BClk_Okay                => BClk_Okay,
    --
    Reg_Updated              => Reg_Updated,
    --
    DP_Addr                  => DP_Addr,
    DP_Wr_Data               => DP_Wr_Data,
    DP_Wr_En                 => DP_Wr_En,
    DP_Rd_Data               => DP_Rd_Data,
    --
    TX_Wr_En                 => TX_Wr_En,
    TX_Wr_Flag               => TX_Wr_Flag,
    TX_Wr_Data               => TX_Wr_Data,
    TX_Req_Next              => TX_Req_Next,
    --
    TX_CRC_Clr               => TX_CRC_Clr,
    TX_CRC_En                => TX_CRC_En,
    TX_CRC_Data              => TX_CRC_Data,
    TX_CRC_Valid             => TX_CRC_Valid,
    --
    RX_Valid                 => RX_Valid,
    RX_Flag                  => RX_Flag,
    RX_Data                  => RX_Data,
    RX_Idle                  => RX_Idle,
    --
    RX_CRC_Clr               => RX_CRC_Clr,
    RX_CRC_En                => RX_CRC_En,
    RX_CRC_Data              => RX_CRC_Data,
    RX_CRC_Valid             => RX_CRC_Valid,
    --
    Interrupt                => Interrupt
  );
 
  U_TX_SER : entity work.sdlc_serial_tx
  generic map(
    Reset_Level              => Reset_Level
  )
  port map(
    Clock                    => Clock,
    Reset                    => Reset,
    --
    BClk_FE                  => BClk_FE,
    BClk_RE                  => BClk_RE,
    BClk_Okay                => BClk_Okay,
    --
    TX_En                    => TX_Wr_En,
    TX_FSS_Flag              => TX_Wr_Flag,
    TX_Data                  => TX_Wr_Data,
    TX_Req_Next              => TX_Req_Next,
    --
    Serial_Out               => SDLC_Out
  );
 
  U_TX_CRC : entity work.sdlc_crc16_ccitt
  generic map(
    Poly_Init                => Poly_Init,
    Reset_Level              => Reset_Level
  )
  port map(
    Clock                    => Clock,
    Reset                    => Reset,
    --
    Clear                    => TX_CRC_Clr,
    Wr_Data                  => TX_Wr_Data,
    Wr_En                    => TX_CRC_En,
    --
    CRC16_Out                => TX_CRC_Data,
    CRC16_Valid              => TX_CRC_Valid
  );
 
  U_RX_SER : entity work.sdlc_serial_rx
  generic map(
    Set_As_Master            => Set_As_Master,
    Clock_Offset             => Clock_Offset,
    Reset_Level              => Reset_Level
  )
  port map(
    Clock                    => Clock,
    Reset                    => Reset,
    --
    BClk_RE                  => BClk_RE,
    BClk_Okay                => BClk_Okay,
    --
    Serial_In                => SDLC_In,
    --
    RX_Valid                 => RX_Valid,
    RX_Flag                  => RX_Flag,
    RX_Data                  => RX_Data,
    RX_Idle                  => RX_Idle
  );
 
  U_RX_CRC : entity work.sdlc_crc16_ccitt
  generic map(
    Poly_Init                => Poly_Init,
    Reset_Level              => Reset_Level
  )
  port map(
    Clock                    => Clock,
    Reset                    => Reset,
    --
    Clear                    => RX_CRC_Clr,
    Wr_Data                  => RX_Data,
    Wr_En                    => RX_CRC_En,
    --
    CRC16_Out                => RX_CRC_Data,
    CRC16_Valid              => RX_CRC_Valid
  );
 
end architecture;