display.vhd

用 vhdl 语言编写的1602的小程序

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;

ENTITY DISPLAY IS
PORT(
		  CLK               : IN STD_LOGIC;
		  RES               : IN STD_LOGIC;
		  DS0               : IN STD_LOGIC;
		  DS1               : IN STD_LOGIC;
		  LCD_RS, LCD_E		: OUT	STD_LOGIC;
		  LCD_RW			: BUFFER STD_LOGIC;
		  DATA_BUS			: INOUT	STD_LOGIC_VECTOR(7 DOWNTO 0)

);
END DISPLAY;

ARCHITECTURE behav OF DISPLAY 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,
	--------------------
	WRITE1_CHAR1,WRITE1_CHAR2,WRITE1_CHAR3,
	WRITE2_CHAR1,WRITE2_CHAR2,WRITE2_CHAR3,
	WRITE3_CHAR1,WRITE3_CHAR2,WRITE3_CHAR3,
	----------------------
	DISPLAY_SET,
	RETURN_HOME,TOGGLE_E, RESET1, RESET2, 
	GOTO_NEXTLINE,
	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_400HZ : STD_LOGIC;
	
	BEGIN
	DATA_BUS <= DATA_BUS_VALUE WHEN LCD_RW = '0' ELSE "ZZZZZZZZ";
	
	
	PROCESS
	BEGIN
	 WAIT UNTIL CLK'EVENT AND CLK = '1';
		IF RES = '1' 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, RES)
	BEGIN
		IF RES = '1' 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

-- 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 <= DISPLAY_SET;

--*************************************************************
--以下是显示模式控制，即通过拨码选择不同的显示内容
--*************************************************************
                WHEN DISPLAY_SET =>
					   IF DS0='0' AND DS1='0' THEN
						state <= TOGGLE_E;
						next_command <= WRITE_CHAR1;
						END IF;
						
					   	IF DS0='1' AND DS1='0' THEN
					    state <= TOGGLE_E;
					    next_command <= WRITE1_CHAR1;
						END IF;
						
						IF DS0='0' AND DS1='1' THEN
					    state <= TOGGLE_E;
					    next_command <= WRITE2_CHAR1;
						END IF;
						
						IF DS0='1' AND DS1='1' THEN
					    state <= TOGGLE_E;
					    next_command <= WRITE3_CHAR1;
					   	END IF;
					
--*****************************************************
--以下是字符显示部分
--*****************************************************
					
--写第一个字符					
				WHEN WRITE_CHAR1 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"30";
						state <= TOGGLE_E;
						next_command <= WRITE_CHAR2;
			
--写第二个字符
				WHEN WRITE_CHAR2 =>
					  LCD_E <= '1';
					  LCD_RS <= '1';
					  LCD_RW <= '0';
					  DATA_BUS_VALUE <= X"31";
					  state <= 	TOGGLE_E;
					  next_command <= WRITE_CHAR3;
--写第三个字符					
				WHEN WRITE_CHAR3 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"32" ;
						state <= TOGGLE_E;
						next_command <= GOTO_NEXTLINE;
--
				WHEN WRITE1_CHAR1 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"33";
						state <= TOGGLE_E;
						next_command <= WRITE1_CHAR2;
-- 
				WHEN WRITE1_CHAR2 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"34";
						state <= TOGGLE_E;
						next_command <= WRITE1_CHAR3;
-- 
				WHEN WRITE1_CHAR3 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"35" ;
						state <= TOGGLE_E;
						next_command <= GOTO_NEXTLINE;	
						
						
						
						
						
				WHEN WRITE2_CHAR1 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"36";
						state <= TOGGLE_E;
						next_command <= WRITE2_CHAR2;
-- 
				WHEN WRITE2_CHAR2 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"37";
						state <= TOGGLE_E;
						next_command <= WRITE2_CHAR3;
-- 
				WHEN WRITE2_CHAR3 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"38" ;
						state <= TOGGLE_E;
						next_command <= GOTO_NEXTLINE;	
						
						
						
						
						
				WHEN WRITE3_CHAR1 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"39";
						state <= TOGGLE_E;
						next_command <= WRITE3_CHAR2;
-- 
				WHEN WRITE3_CHAR2 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"3a";
						state <= TOGGLE_E;
						next_command <= WRITE3_CHAR3;
-- 
				WHEN WRITE3_CHAR3 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"3b" ;
						state <= TOGGLE_E;
						next_command <= GOTO_NEXTLINE;	
						
						
						
						
						
									
				
-- 
				WHEN WRITE_CHAR4 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"20";
						state <= TOGGLE_E;
						next_command <= WRITE_CHAR5;
-- 
				WHEN WRITE_CHAR5 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"34";
						state <= TOGGLE_E;
						next_command <= WRITE_CHAR6;
-- 
				WHEN WRITE_CHAR6 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"38" ;
						state <= TOGGLE_E;
						next_command <= WRITE_CHAR7;
--
				WHEN WRITE_CHAR7 =>
						LCD_E <= '1';
						LCD_RS <= '1';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"4D";
						state <= TOGGLE_E;
						next_command <= RETURN_HOME;
						
--换行
				WHEN GOTO_NEXTLINE =>
						LCD_E <= '1';
						LCD_RS <= '0';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"C0";
						state <= TOGGLE_E;
						next_command <= WRITE_CHAR4;
						
-- 回到开头
            	WHEN RETURN_HOME =>
						LCD_E <= '1';
						LCD_RS <= '0';
						LCD_RW <= '0';
						DATA_BUS_VALUE <= X"80";
						state <= TOGGLE_E;
						next_command <= DISPLAY_SET;
-- 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;

	END behav;