ALTERA USB BLASTER自制全套资料[uC技术交流社区]

我不明白这个程序里面分成的几个状态是什么 ??希望高手赐教谢谢

LIBRARY ieee;
USE ieee.std_logic_1164.all;
USE ieee.std_logic_unsigned.all;

ENTITY jtag_logic IS
PORT
(
  CLK : IN STD_LOGIC;        -- external 24/25 MHz oscillator
  nRXF : IN STD_LOGIC;       -- FT245BM nRXF
  nTXE : IN STD_LOGIC;       -- FT245BM nTXE
  B_TDO : IN STD_LOGIC;      -- JTAG input: TDO of last device in chain
  nRD : OUT STD_LOGIC;       -- FT245BM nRD
  WR : OUT STD_LOGIC;        -- FT245BM WR
  B_TCK : BUFFER STD_LOGIC; -- JTAG output: TCK to chain
  B_TMS : BUFFER STD_LOGIC; -- JTAG output: TMS to chain
  B_TDI : BUFFER STD_LOGIC; -- JTAG output: to TDI of first device in chain
  D : INOUT STD_LOGIC_VECTOR(7 downto 0) -- FT245BM D[7..0]
);
END jtag_logic;

ARCHITECTURE spec OF jtag_logic IS
TYPE states IS
(
  wait_for_nRXF_low,
  set_nRD_low,
  keep_nRD_low,
  latch_data_from_host,
  set_nRD_high,
  bits_set_pins_from_data,
  bytes_set_bitcount,
  bytes_get_tdo_set_tdi,
  bytes_clock_high_and_shift,
  bytes_keep_clock_high,
  bytes_clock_finish,
  wait_for_nTXE_low,
  set_WR_high,
  output_enable,
  set_WR_low,
  output_disable
);

SIGNAL carry: STD_LOGIC;
SIGNAL do_output: STD_LOGIC;
SIGNAL ioshifter: STD_LOGIC_VECTOR(7 DOWNTO 0);
SIGNAL bitcount: STD_LOGIC_VECTOR(8 DOWNTO 0);
SIGNAL state, next_state: states;

BEGIN
-- sm: PROCESS(nRXF, nTXE, state, D, bitcount, ioshifter, do_output)
sm: PROCESS(nRXF, nTXE, state, bitcount, ioshifter, do_output)

BEGIN
  CASE state IS

   -- ============================ INPUT

   WHEN wait_for_nRXF_low =>
    IF nRXF='0' THEN
     next_state <= set_nRD_low;
    ELSE
     next_state <= wait_for_nRXF_low;
    END IF;

   WHEN set_nRD_low =>
    next_state <= keep_nRD_low;

   WHEN keep_nRD_low =>
    next_state <= latch_data_from_host;

   WHEN latch_data_from_host =>
    next_state <= set_nRD_high;

   WHEN set_nRD_high =>
    IF NOT (bitcount(8 DOWNTO 3) = "000000") THEN
     next_state <= bytes_get_tdo_set_tdi;
    ELSIF ioshifter(7) = '1' THEN
     next_state <= bytes_set_bitcount;
    ELSE
     next_state <= bits_set_pins_from_data;
    END IF;

   WHEN bytes_set_bitcount =>
    next_state <= wait_for_nRXF_low;

   -- ============================ BIT BANGING

   WHEN bits_set_pins_from_data =>
    IF ioshifter(6) = '0' THEN
     next_state <= wait_for_nRXF_low; -- read next byte from host
    ELSE
     next_state <= wait_for_nTXE_low; -- output byte to host
    END IF;

   -- ============================ BYTE OUTPUT (SHIFT OUT 8 BITS)

   WHEN bytes_get_tdo_set_tdi =>
    next_state <= bytes_clock_high_and_shift;

   WHEN bytes_clock_high_and_shift =>
    next_state <= bytes_keep_clock_high;

   WHEN bytes_keep_clock_high =>
    next_state <= bytes_clock_finish;

   WHEN bytes_clock_finish =>
    IF NOT (bitcount(2 DOWNTO 0) = "111") THEN
     next_state <= bytes_get_tdo_set_tdi; -- clock next bit
    ELSIF do_output = '1' THEN
     next_state <= wait_for_nTXE_low; -- output byte to host
    ELSE
     next_state <= wait_for_nRXF_low; -- read next byte from host
    END IF;

   -- ============================ OUTPUT BYTE TO HOST

   WHEN wait_for_nTXE_low =>
    IF nTXE = '0' THEN
     next_state <= set_WR_high;
    ELSE
     next_state <= wait_for_nTXE_low;
    END IF;

   WHEN set_WR_high =>
    next_state <= output_enable;

   WHEN output_enable =>
    next_state <= set_WR_low;

   WHEN set_WR_low =>
    next_state <= output_disable;

   WHEN output_disable =>
    next_state <= wait_for_nRXF_low; -- read next byte from host

   WHEN OTHERS =>
    next_state <= wait_for_nRXF_low;

  END CASE;
END PROCESS sm;

out_sm: PROCESS(CLK, state, ioshifter, B_TDO, bitcount, carry)

BEGIN
  IF CLK = '1' AND CLK'event THEN

   IF state = set_nRD_low OR state = keep_nRD_low OR state = latch_data_from_host THEN
    nRD <= '0';
   ELSE
    nRD <= '1';
   END IF;

   IF state = latch_data_from_host THEN
    ioshifter(7 DOWNTO 0) <= D;
   END IF;

   IF state = set_WR_high OR state = output_enable THEN
    WR <= '1';
   ELSE
    WR <= '0';
   END IF;

   IF state = output_enable OR state = set_WR_low THEN
    D <= ioshifter(7 DOWNTO 0);
   ELSE
    D <= "ZZZZZZZZ";
   END IF;

   IF state = bits_set_pins_from_data THEN
    B_TDI <= ioshifter(4);
    B_TMS <= ioshifter(1);
    B_TCK <= ioshifter(0);
    ioshifter <= "0000001" & B_TDO;
   END IF;

   IF state = bytes_set_bitcount THEN
    bitcount <= ioshifter(5 DOWNTO 0) & "111";
    do_output <= ioshifter(6);
   END IF;

   IF state = bytes_get_tdo_set_tdi THEN
    carry <= B_TDO;
    B_TDI <= ioshifter(0);
    bitcount <= bitcount - 1;
   END IF;

   IF state = bytes_clock_high_and_shift OR state = bytes_keep_clock_high THEN
    B_TCK <= '1';
   END IF;

   IF state = bytes_clock_high_and_shift THEN
    ioshifter <= carry & ioshifter(7 DOWNTO 1);
   END IF;

   IF state = bytes_clock_finish THEN
    B_TCK <= '0';
   END IF;

   state <= next_state;

  END IF;
END PROCESS out_sm;

END spec;

主题：ALTERA USB BLASTER自制全套资料