lcd_controller.vhd


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

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--

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--   FileName:         lcd_controller.vhd

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--   Dependencies:     none

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--   Design Software:  Quartus II 32-bit Version 11.1 Build 173 SJ Full Version

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--

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--   HDL CODE IS PROVIDED "AS IS."  DIGI-KEY EXPRESSLY DISCLAIMS ANY

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--   WARRANTY OF ANY KIND, WHETHER EXPRESS OR IMPLIED, INCLUDING BUT NOT

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--   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A

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--   PARTICULAR PURPOSE, OR NON-INFRINGEMENT. IN NO EVENT SHALL DIGI-KEY

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--   BE LIABLE FOR ANY INCIDENTAL, SPECIAL, INDIRECT OR CONSEQUENTIAL

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--   DAMAGES, LOST PROFITS OR LOST DATA, HARM TO YOUR EQUIPMENT, COST OF

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--   PROCUREMENT OF SUBSTITUTE GOODS, TECHNOLOGY OR SERVICES, ANY CLAIMS

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--   BY THIRD PARTIES (INCLUDING BUT NOT LIMITED TO ANY DEFENSE THEREOF),

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--   ANY CLAIMS FOR INDEMNITY OR CONTRIBUTION, OR OTHER SIMILAR COSTS.

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--

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--   Version History

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--   Version 1.0 6/2/2006 Scott Larson

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--     Initial Public Release

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--    Version 2.0 6/13/2012 Scott Larson

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--

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--   CLOCK FREQUENCY: to change system clock frequency, change Line 65

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--

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--   LCD INITIALIZATION SETTINGS: to change, comment/uncomment lines:

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--

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--   Function Set  

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--      2-line mode, display on             Line 93    lcd_data <= "00111100";

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--      1-line mode, display on             Line 94    lcd_data <= "00110100";

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--      1-line mode, display off            Line 95    lcd_data <= "00110000";

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--      2-line mode, display off            Line 96    lcd_data <= "00111000";

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--   Display ON/OFF

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--      display on, cursor off, blink off   Line 104   lcd_data <= "00001100";

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--      display on, cursor off, blink on    Line 105   lcd_data <= "00001101";

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--      display on, cursor on, blink off    Line 106   lcd_data <= "00001110";

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--      display on, cursor on, blink on     Line 107   lcd_data <= "00001111";

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--      display off, cursor off, blink off  Line 108   lcd_data <= "00001000";

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--      display off, cursor off, blink on   Line 109   lcd_data <= "00001001";

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--      display off, cursor on, blink off   Line 110   lcd_data <= "00001010";

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--      display off, cursor on, blink on    Line 111   lcd_data <= "00001011";

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--   Entry Mode Set

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--      increment mode, entire shift off    Line 127   lcd_data <= "00000110";

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--      increment mode, entire shift on     Line 128   lcd_data <= "00000111";

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--      decrement mode, entire shift off    Line 129   lcd_data <= "00000100";

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--      decrement mode, entire shift on     Line 130   lcd_data <= "00000101";

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--    

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

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LIBRARY ieee;

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USE ieee.std_logic_1164.ALL;

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ENTITY lcd_controller IS

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  PORT(

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    clk        : IN    STD_LOGIC;  --system clock

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    reset_n    : IN    STD_LOGIC;  --active low reinitializes lcd

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    lcd_enable : IN    STD_LOGIC;  --latches data into lcd controller

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    lcd_bus    : IN    STD_LOGIC_VECTOR(9 DOWNTO 0);  --data and control signals

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    busy       : OUT   STD_LOGIC := '1';  --lcd controller busy/idle feedback

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    rw, rs, e  : OUT   STD_LOGIC;  --read/write, setup/data, and enable for lcd

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    lcd_data   : OUT   STD_LOGIC_VECTOR(7 DOWNTO 0); --data signals for lcd

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   mr_debug   : OUT    STD_LOGIC_VECTOR(3 DOWNTO 0)

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   );

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END lcd_controller;

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ARCHITECTURE controller OF lcd_controller IS

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  TYPE CONTROL IS(power_up, initialize, ready, send);

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  SIGNAL    state      : CONTROL;

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  CONSTANT  freq       : INTEGER := 50; --system clock frequency in MHz

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BEGIN

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  PROCESS(clk)

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    VARIABLE clk_count : INTEGER := 0; --event counter for timing

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  BEGIN

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  IF(clk'EVENT and clk = '1') THEN

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      CASE state IS

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        --wait 50 ms to ensure Vdd has risen and required LCD wait is met

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        WHEN power_up =>

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          busy <= '1';

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          IF(clk_count < (5 * freq)) THEN    --wait 50 ms    (50000 * freq)) 

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            clk_count := clk_count + 1;

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            state <= power_up;

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        lcd_data <= "00000001";

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          ELSE                                   --power-up complete

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            clk_count := 0;

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            rs <= '0';

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            rw <= '0';

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            lcd_data <= "00110000";

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            state <= initialize;

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          END IF;

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        --cycle through initialization sequence  

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        WHEN initialize =>

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          busy <= '1';

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          clk_count := clk_count + 1;

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          IF(clk_count < (10 * freq)) THEN       --function set

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            lcd_data <= "00111100";      --2-line mode, display on

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            --lcd_data <= "00110100";    --1-line mode, display on

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            --lcd_data <= "00110000";    --1-line mdoe, display off

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            --lcd_data <= "00111000";    --2-line mode, display off

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            e <= '1';

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            state <= initialize;

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          ELSIF(clk_count < (1 * freq)) THEN    --wait 50 us    (60 * freq))

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            lcd_data <= "00000000";

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            e <= '0';

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            state <= initialize;

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          ELSIF(clk_count < (1 * freq)) THEN    --display on/off control    < (70 * freq)) 

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            lcd_data <= "00001100";      --display on, cursor off, blink off

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            --lcd_data <= "00001101";    --display on, cursor off, blink on

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            --lcd_data <= "00001110";    --display on, cursor on, blink off

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            --lcd_data <= "00001111";    --display on, cursor on, blink on

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            --lcd_data <= "00001000";    --display off, cursor off, blink off

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            --lcd_data <= "00001001";    --display off, cursor off, blink on

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            --lcd_data <= "00001010";    --display off, cursor on, blink off

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            --lcd_data <= "00001011";    --display off, cursor on, blink on            

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            e <= '1';

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            state <= initialize;

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          ELSIF(clk_count < (1 * freq)) THEN   --wait 50 us   (120 * freq))

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            lcd_data <= "00000000";

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            e <= '0';

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            state <= initialize;

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          ELSIF(clk_count < (1 * freq)) THEN   --display clear    (130 * freq))

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            lcd_data <= "00000001";

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            e <= '1';

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            state <= initialize;

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          ELSIF(clk_count < (1 * freq)) THEN  --wait 2 ms    (2130 * freq))

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            lcd_data <= "00000000";

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            e <= '0';

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            state <= initialize;

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          ELSIF(clk_count < (1 * freq)) THEN  --entry mode set      (2140 * freq))

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            lcd_data <= "00000110";      --increment mode, entire shift off

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            --lcd_data <= "00000111";    --increment mode, entire shift on

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            --lcd_data <= "00000100";    --decrement mode, entire shift off

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            --lcd_data <= "00000101";    --decrement mode, entire shift on

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            e <= '1';

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            state <= initialize;

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          ELSIF(clk_count < (1 * freq)) THEN  --wait 60 us       (2200 * freq))

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            lcd_data <= "00000000";

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            e <= '0';

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            state <= initialize;

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          ELSE                                   --initialization complete

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            clk_count := 0;

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            busy <= '0';

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            state <= ready;

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          END IF;    

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        --wait for the enable signal and then latch in the instruction

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        WHEN ready =>

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          IF(lcd_enable = '1') THEN

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            busy <= '1';

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            rs <= lcd_bus(9);

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            rw <= lcd_bus(8);

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            lcd_data <= lcd_bus(7 DOWNTO 0);

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            clk_count := 0;            

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            state <= send;

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          ELSE

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            busy <= '0';

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            rs <= '0';

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            rw <= '0';

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            lcd_data <= "00000000";

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            clk_count := 0;

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            state <= ready;

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          END IF;

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        --send instruction to lcd        

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        WHEN send =>

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        busy <= '1';

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        IF(clk_count < (50 * freq)) THEN  --do not exit for 50us

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           busy <= '1';

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           IF(clk_count < freq) THEN      --negative enable

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            e <= '0';

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           ELSIF(clk_count < (14 * freq)) THEN  --positive enable half-cycle

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            e <= '1';

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           ELSIF(clk_count < (27 * freq)) THEN  --negative enable half-cycle

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            e <= '0';

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           END IF;

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           clk_count := clk_count + 1;

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           state <= send;

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        ELSE

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          clk_count := 0;

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          state <= ready;

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        END IF;

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      END CASE;    

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      --reset

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      IF(reset_n = '0') THEN

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          state <= power_up;

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      END IF;

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    --mr Debug

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    IF (state = Power_up) THEN 

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    mr_debug <="0001";

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    ELSIF (state = initialize) THEN 

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    mr_debug <="0010";

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    ELSIF (state = ready) THEN 

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    mr_debug <="0100";

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    ELSIF (state = send) THEN 

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    mr_debug <="1000";

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    END IF;

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    END IF;

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  END PROCESS;

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END controller;