LIBRARY IEEE;
USE  IEEE.STD_LOGIC_1164.all;
USE  IEEE.STD_LOGIC_ARITH.all;
USE  IEEE.STD_LOGIC_UNSIGNED.all;
-- This code displays time in the UP3's LCD Display
-- SW8 (GLOBAL RESET) resets time
ENTITY UP3_CLOCK IS
	PORT(reset, clk_48Mhz				: IN	STD_LOGIC;
		 LCD_RS, LCD_E, RESET_LED, SEC_LED		: OUT	STD_LOGIC;
		 LCD_RW						: BUFFER STD_LOGIC;
		 DATA_BUS				: INOUT	STD_LOGIC_VECTOR(7 DOWNTO 0));
END UP3_CLOCK;

ARCHITECTURE a OF UP3_CLOCK IS
	TYPE STATE_TYPE IS (HOLD, FUNC_SET, DISPLAY_ON, MODE_SET, WRITE_CHAR1,
	WRITE_CHAR2,WRITE_CHAR3,WRITE_CHAR4,WRITE_CHAR5,WRITE_CHAR6,WRITE_CHAR7,
	WRITE_CHAR8, WRITE_CHAR9, WRITE_CHAR10, RETURN_HOME, TOGGLE_E, RESET1, RESET2, 
	RESET3, DISPLAY_OFF, DISPLAY_CLEAR);
	SIGNAL state, next_command: STATE_TYPE;
	SIGNAL DATA_BUS_VALUE: STD_LOGIC_VECTOR(7 DOWNTO 0);
	SIGNAL CLK_COUNT_400HZ: STD_LOGIC_VECTOR(19 DOWNTO 0);
	SIGNAL CLK_COUNT_10HZ: STD_LOGIC_VECTOR(7 DOWNTO 0);
	SIGNAL BCD_SECD0,BCD_SECD1,BCD_MIND0,BCD_MIND1: STD_LOGIC_VECTOR(3 DOWNTO 0);
	SIGNAL BCD_HRD0,BCD_HRD1,BCD_TSEC: STD_LOGIC_VECTOR(3 DOWNTO 0);
	SIGNAL CLK_400HZ, CLK_10HZ : STD_LOGIC;
BEGIN
	RESET_LED <= NOT RESET;
	SEC_LED <= BCD_SECD0(0);
-- BIDIRECTIONAL TRI STATE LCD DATA BUS
	DATA_BUS <= DATA_BUS_VALUE WHEN LCD_RW = '0' ELSE "ZZZZZZZZ";

	PROCESS
	BEGIN
	 WAIT UNTIL CLK_48MHZ'EVENT AND CLK_48MHZ = '1';
		IF RESET = '0' THEN
		 CLK_COUNT_400HZ <= X"00000";
		 CLK_400HZ <= '0';
		ELSE
				IF CLK_COUNT_400HZ < X"0EA60" THEN 
				 CLK_COUNT_400HZ <= CLK_COUNT_400HZ + 1;
				ELSE
		    	 CLK_COUNT_400HZ <= X"00000";
				 CLK_400HZ <= NOT CLK_400HZ;
				END IF;
		END IF;
	END PROCESS;
	PROCESS (CLK_400HZ, reset)
	BEGIN
		IF reset = '0' THEN
			state <= RESET1;
			DATA_BUS_VALUE <= X"38";
			next_command <= RESET2;
			LCD_E <= '1';
			LCD_RS <= '0';
			LCD_RW <= '0';

		ELSIF CLK_400HZ'EVENT AND CLK_400HZ = '1' THEN
-- GENERATE 1 SEC CLOCK SIGNAL FOR SECOND COUNT PROCESS
			IF CLK_COUNT_10HZ < 19 THEN
				CLK_COUNT_10HZ <= CLK_COUNT_10HZ + 1;
			ELSE
				CLK_COUNT_10HZ <= X"00";
				CLK_10HZ <= NOT CLK_10HZ;
			END IF;
-- SEND TIME TO LCD			
			CASE state IS
-- Set Function to 8-bit transfer and 2 line display with 5x8 Font size
-- see Hitachi HD44780 family data sheet for LCD command and timing details
				WHEN RESET1 =>
						LCD_E <= '1';
						LCD_RS <= '0';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"38";
						state <= TOGGLE_E;
						next_command <= RESET2;
				WHEN RESET2 =>
						LCD_E <= '1';
						LCD_RS <= '0';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"38";
						state <= TOGGLE_E;
						next_command <= RESET3;
				WHEN RESET3 =>
						LCD_E <= '1';
						LCD_RS <= '0';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"38";
						state <= TOGGLE_E;
						next_command <= FUNC_SET;
-- EXTRA STATES ABOVE ARE NEEDED FOR RELIABLE PUSHBUTTON RESET OF LCD
				WHEN FUNC_SET =>
						LCD_E <= '1';
						LCD_RS <= '0';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"38";
						state <= TOGGLE_E;
						next_command <= DISPLAY_OFF;
-- Turn off Display and Turn off cursor
				WHEN DISPLAY_OFF =>
						LCD_E <= '1';
						LCD_RS <= '0';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"08";
						state <= TOGGLE_E;
						next_command <= DISPLAY_CLEAR;
-- Turn on Display and Turn off cursor
				WHEN DISPLAY_CLEAR =>
						LCD_E <= '1';
						LCD_RS <= '0';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"01";
						state <= TOGGLE_E;
						next_command <= DISPLAY_ON;
-- Turn on Display and Turn off cursor
				WHEN DISPLAY_ON =>
						LCD_E <= '1';
						LCD_RS <= '0';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"0C";
						state <= TOGGLE_E;
						next_command <= MODE_SET;
-- Set write mode to auto increment address and move cursor to the right
				WHEN MODE_SET =>
						LCD_E <= '1';
						LCD_RS <= '0';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"06";
						state <= TOGGLE_E;
						next_command <= WRITE_CHAR1;
-- Write ASCII hex character in first LCD character location
				WHEN WRITE_CHAR1 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"3" & BCD_HRD1;
						state <= TOGGLE_E;
						next_command <= WRITE_CHAR2;
-- Write ASCII hex character in second LCD character location
				WHEN WRITE_CHAR2 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"3" & BCD_HRD0;
						state <= TOGGLE_E;
						next_command <= WRITE_CHAR3;
-- Write ASCII hex character in third LCD character location
				WHEN WRITE_CHAR3 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"3A" ;
						state <= TOGGLE_E;
						next_command <= WRITE_CHAR4;
-- Write ASCII hex character in fourth LCD character location
				WHEN WRITE_CHAR4 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"3" & BCD_MIND1;
						state <= TOGGLE_E;
						next_command <= WRITE_CHAR5;
-- Write ASCII hex character in fifth LCD character location
				WHEN WRITE_CHAR5 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"3" & BCD_MIND0;
						state <= TOGGLE_E;
						next_command <= WRITE_CHAR6;
-- Write ASCII hex character in sixth LCD character location
				WHEN WRITE_CHAR6 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"3A" ;
						state <= TOGGLE_E;
						next_command <= WRITE_CHAR7;
-- Write ASCII hex character in seventh LCD character location
				WHEN WRITE_CHAR7 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"3" & BCD_SECD1;
						state <= TOGGLE_E;
						next_command <= WRITE_CHAR8;
-- Write ASCII hex character in eighth LCD character location
				WHEN WRITE_CHAR8 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"3" & BCD_SECD0;
						state <= TOGGLE_E;
						next_command <= WRITE_CHAR9;
				WHEN WRITE_CHAR9 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"2E";
						state <= TOGGLE_E;
						next_command <= WRITE_CHAR10;
				WHEN WRITE_CHAR10 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"3" & BCD_TSEC;
						state <= TOGGLE_E;
						next_command <= RETURN_HOME;

-- Return write address to first character postion
				WHEN RETURN_HOME =>
						LCD_E <= '1';
						LCD_RS <= '0';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"80";
						state <= TOGGLE_E;
						next_command <= WRITE_CHAR1;
-- The next two states occur at the end of each command to the LCD
-- Toggle E line - falling edge loads inst/data to LCD controller
				WHEN TOGGLE_E =>
						LCD_E <= '0';
						state <= HOLD;
-- Hold LCD inst/data valid after falling edge of E line				
				WHEN HOLD =>
						state <= next_command;
			END CASE;
		END IF;
	END PROCESS;
	PROCESS (Clk_10hz, reset)
	BEGIN
		IF reset = '0' THEN	
			BCD_HRD1 <= X"0";			
			BCD_HRD0 <= X"0";
			BCD_MIND1 <= X"0";
			BCD_MIND0 <= X"0";
			BCD_SECD1 <= X"0";
			BCD_SECD0 <= X"0";
			BCD_TSEC  <= X"0";

		ELSIF clk_10HZ'EVENT AND clk_10HZ = '1' THEN
-- TENTHS OF SECONDS
		IF BCD_TSEC < 9 THEN
		 BCD_TSEC <= BCD_TSEC + 1;
		ELSE
		 BCD_TSEC <= X"0";
-- SECONDS
		IF BCD_SECD0 < 9 THEN
	 	 BCD_SECD0 <= BCD_SECD0 + 1;
		ELSE
-- TENS OF SECONDS
		 BCD_SECD0 <= "0000";
	 	  IF BCD_SECD1 < 5 THEN
	  	 BCD_SECD1 <= BCD_SECD1 + 1;
	 	 ELSE
-- MINUTES
	  	 BCD_SECD1 <= "0000";
	  	 IF BCD_MIND0 < 9 THEN
	   	  BCD_MIND0 <= BCD_MIND0 + 1;
	  	 ELSE
-- TENS OF MINUTES
	   	  BCD_MIND0 <= "0000";
	   	  IF BCD_MIND1 < 5 THEN
	       BCD_MIND1 <= BCD_MIND1 + 1;
	   	  ELSE
-- HOURS
	    	BCD_MIND1 <= "0000";
	    	IF BCD_HRD0 < 9 AND NOT((BCD_HRD1 = 2) AND (BCD_HRD0 = 3))THEN
	     	 BCD_HRD0 <= BCD_HRD0 + 1;
	    	ELSE
-- TENS OF HOURS
	     	 IF NOT((BCD_HRD1 = 2) AND (BCD_HRD0 = 3)) THEN
	      	  BCD_HRD1 <= BCD_HRD1 + 1;
	      	  BCD_HRD0 <= "0000";
	     	 ELSE
-- NEW DAY
	      	 BCD_HRD1 <= "0000";
          	 BCD_HRD0 <= "0000";
         	END IF;
           END IF;
          END IF;
         END IF;
        END IF;
       END IF;
	 END IF;
	END IF;
 END PROCESS;
END a;