rtl/vhdl/c4m_jtag_tap_controller.vhdl

   1 -- A JTAG complient tap controller implementation
   2 -- This is implemented based on the IEEE 1149.1 standard
   3
   4 library ieee;
   5 use ieee.std_logic_1164.ALL;
   6
   7 use work.c4m_jtag.ALL;
   8
   9 entity c4m_jtag_tap_controller is
  10   generic (
  11     IR_WIDTH:   integer := 2;
  12     IOS:        integer := 1;
  13
  14     VERSION:    std_logic_vector(3 downto 0)
  15   );
  16   port (
  17     -- The TAP signals
  18     TCK:        in std_logic;
  19     TMS:        in std_logic;
  20     TDI:        in std_logic;
  21     TDO:        out std_logic;
  22     TDO_EN:     out std_logic;
  23     TRST_N:     in std_logic;
  24
  25     -- The FSM state indicators
  26     STATE:      out TAPSTATE_TYPE;
  27     NEXT_STATE: out TAPSTATE_TYPE;
  28     DRSTATE:    out std_logic;
  29
  30     -- The Instruction Register
  31     IR:         out std_logic_vector(IR_WIDTH-1 downto 0);
  32
  33     -- The I/O access ports
  34     CORE_IN:    out std_logic_vector(IOS-1 downto 0);
  35     CORE_EN:    in std_logic_vector(IOS-1 downto 0);
  36     CORE_OUT:   in std_logic_vector(IOS-1 downto 0);
  37
  38     -- The pad connections
  39     PAD_IN:     in std_logic_vector(IOS-1 downto 0);
  40     PAD_EN:     out std_logic_vector(IOS-1 downto 0);
  41     PAD_OUT:    out std_logic_vector(IOS-1 downto 0)
  42   );
  43 end c4m_jtag_tap_controller;
  44
  45 architecture rtl of c4m_jtag_tap_controller is
  46   signal S_STATE:       TAPSTATE_TYPE;
  47   signal S_NEXT_STATE:  TAPSTATE_TYPE;
  48   signal S_IRSTATE:     std_logic;
  49   signal S_DRSTATE:     std_logic;
  50   signal S_IR:          std_logic_vector(IR_WIDTH-1 downto 0);
  51
  52   signal IR_TDO:        std_logic;
  53   signal IR_TDO_EN:     std_logic;
  54   signal ID_TDO:        std_logic;
  55   signal ID_TDO_EN:     std_logic;
  56   signal IO_TDO:        std_logic;
  57   signal IO_TDO_EN:     std_logic;
  58   signal EN:            std_logic_vector(2 downto 0) := "000";
  59
  60   -- TODO: Automate PART_NUMBER generation
  61   constant PART_NUMBER: std_logic_vector(15 downto 0) := "0000000010001001";
  62   -- TODO: Get manufacturer ID
  63   constant MANUFACTURER: std_logic_vector(10 downto 0) := "00000000000";
  64 begin
  65   STATE <= S_STATE;
  66   NEXT_STATE <= S_NEXT_STATE;
  67   DRSTATE <= S_DRSTATE;
  68   IR <= S_IR;
  69
  70   -- JTAG state machine
  71   FSM:  c4m_jtag_tap_fsm
  72     port map (
  73       TCK => TCK,
  74       TMS => TMS,
  75       TRST_N => TRST_N,
  76       STATE => S_STATE,
  77       NEXT_STATE => S_NEXT_STATE,
  78       DRSTATE => S_DRSTATE,
  79       IRSTATE => S_IRSTATE
  80     );
  81
  82   -- The instruction register
  83   IRBLOCK: c4m_jtag_irblock
  84     generic map (
  85       IR_WIDTH => IR_WIDTH
  86     )
  87     port map (
  88       TCK => TCK,
  89       TDI => TDI,
  90       TDO => IR_TDO,
  91       TDO_EN => IR_TDO_EN,
  92       STATE => S_STATE,
  93       NEXT_STATE => S_NEXT_STATE,
  94       IRSTATE => S_IRSTATE,
  95       IR => S_IR
  96     );
  97
  98   -- The ID
  99   IDBLOCK: c4m_jtag_idblock
 100     generic map (
 101       IR_WIDTH => IR_WIDTH,
 102       PART_NUMBER => PART_NUMBER,
 103       MANUFACTURER => MANUFACTURER
 104     )
 105     port map (
 106       TCK => TCK,
 107       TDI => TDI,
 108       TDO => ID_TDO,
 109       TDO_EN => ID_TDO_EN,
 110       STATE => S_STATE,
 111       NEXT_STATE => S_NEXT_STATE,
 112       DRSTATE => S_DRSTATE,
 113       IR => S_IR
 114     );
 115
 116   -- The IOS
 117   IOBLOCK: c4m_jtag_ioblock
 118     generic map (
 119       IR_WIDTH => IR_WIDTH,
 120       IOS => IOS
 121     )
 122     port map (
 123       TCK => TCK,
 124       TDI => TDI,
 125       TDO => IO_TDO,
 126       TDO_EN => IO_TDO_EN,
 127       STATE => S_STATE,
 128       NEXT_STATE => S_NEXT_STATE,
 129       DRSTATE => S_DRSTATE,
 130       IR => S_IR,
 131       CORE_OUT => CORE_OUT,
 132       CORE_IN => CORE_IN,
 133       CORE_EN => CORE_EN,
 134       PAD_OUT => PAD_OUT,
 135       PAD_IN => PAD_IN,
 136       PAD_EN => PAD_EN
 137     );
 138
 139   TDO <= IR_TDO when IR_TDO_EN = '1' else
 140          ID_TDO when ID_TDO_EN = '1' else
 141          IO_TDO when IO_TDO_EN = '1' else
 142          '0';
 143   TDO_EN <= IR_TDO_EN or ID_TDO_EN or IO_TDO_EN;
 144
 145   EN <= IR_TDO_EN & ID_TDO_EN & IO_TDO_EN;
 146   assert EN = "000" or EN = "100" or EN = "010" or EN = "001"
 147     report "TDO conflict in c4m_jtag_tap_controller"
 148     severity ERROR;
 149 end rtl;
 150
 151