1. Software Environment ISE 5.x Interaction with simple LCDs
Tutorial - LCD
Xilinx Integrated
Software Environment ISE 5.x
Interaction with simple LCDs
Authors: V.Sklyarov, I.Skliarova
Copyright (c) 2003 by Valery Sklyarov and Iouliia Skliarova: DETUA, IEETA, Aveiro University, Portugal

2. HD44780U Dot Matrix LCD Controller/Driver
Expansion
connector
Two LCDs can
function at the
same time
LCD control
KS0073 Driver & Controller for dot matrix LCD

3. Connections GND ext_a<0> (FPGA pin H14) 5V cs_lcd (FPGA pin A9)
Expansion
connector
see manual on EA DIP 204-4
(Electronic Assembly - Germany)
see Spartan IIE development
platform (Trenz Electronic - Germany)
GND
ext_a<0> (FPGA pin H14) 5V
cs_lcd (FPGA pin A9)
contrast
resistor
ext_rw (FPGA pin D16)
GND

4. NET "clk48in" TNM_NET = "clk48in";
TIMESPEC "TS_clk48in" = PERIOD "clk48in" 48 MHz HIGH 50 %;
NET "clk48in" LOC = "t9";
NET "init" LOC = "p15";
NET "ext_a<2>" LOC = "H15";
NET "ext_a<1>" LOC = "F16";
NET "ext_a<0>" LOC = "H13";
NET "csn_lcd" LOC = "G14";
NET "cs_lcd" LOC = "G13";
NET "ext_d<2>" LOC = "D15";
NET "ext_rw" LOC = "D16";
NET "ext_d<6>" LOC = "F13";
NET "ext_d<4>" LOC = "E14";
NET "ext_d<0>" LOC = "C16";
NET "ext_d<7>" LOC = "G12";
NET "ext_d<5>" LOC = "F12";
NET "ext_d<3>" LOC = "E13";
NET "ext_d<1>" LOC = "D14";
NET "cpld_cs" LOC = "m16";
NET "cpld_rw" LOC = "m15";
NET "a<1>" LOC = "t10";
NET "a<2>" LOC = "m10";
NET "d<0>" LOC = "b16";
NET "d<1>" LOC = "e15";
NET "d<2>" LOC = "f14";
NET "d<3>" LOC = "G15";
NET "d<4>" LOC = "J14";
NET "d<5>" LOC = "L13";
NET "d<6>" LOC = "L16";
NET "d<7>" LOC = "P16";

5. Example 1 library IEEE; use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
entity Hitachi_lcd is
port (
cpld_rw: inout std_logic;
cpld_cs: out std_logic;
a : out std_logic_vector(2 downto 1);
d : inout std_logic_vector(7 downto 0);
clk : in std_logic; -- clock 48 MHz
rst : in std_logic; -- reset
ext_a : out std_logic_vector(2 downto 0); -- LCD control
ext_d : out std_logic_vector(7 downto 0); -- LCD data
ext_rw : out std_logic; LCD read/write
cs_lcd : out std_logic; LCD chip select active high
csn_lcd : out std_logic LCD data direction );
end Hitachi_lcd;

6. signal div: unsigned (20 downto 0);
architecture Behavioral of Hitachi_lcd is
signal state : std_logic_vector(3 downto 0);
signal lled : std_logic_vector(7 downto 0); onboard leds (3 downto 0)
signal lpb : std_logic_vector(7 downto 0); -- onboard pushbuttons
signal dipswitch : std_logic_vector(7 downto 0);
signal clk: std_logic; local clock
signal div: unsigned (16 downto 0); -- local clock divider
signal reset: std_logic; -- lcd reset sequence active
signal cmd: std_logic_vector (7 downto 0); -- data/command to lcd
signal rs: std_logic; register select bit for lcd
signal idx: integer range 0 to 3; -- sequencer index for lcd timing
signal cs: std_logic; chip select for lcd
signal cnt: unsigned (5 downto 0); -- character, command counter
constant line1: string(1 to 16):= "LCD operations :"; strings to display
constant line2: string(1 to 4):= "DEMO";
begin
process(clk48, rst) -- local clock generator
if rst= '1' then
div <= (others=> '0');
elsif rising_edge(clk48) then
div<= div + 1;
end if;
end process;
clk<= div(div'left);
-- the following blue text is included just in order to read dip switchers through CPLD
-- see tutorial 2 for details
signal div: unsigned (20 downto 0);
This line can be changed as follows
in order to see how each character
is displayed from left to right

7. process(clk48, rst)
begin
if rst= '1' then
state<= (others=> '0');
elsif rising_edge(clk48) then
state<= state + 1;
end if;
end process;
cpld_cs <= '1';
case state is
when "0000" => a <= "00"; -- address = 00 => push buttons
cpld_rw <= '1'; -- read from cpld
when "0001" => cpld_cs <= '0'; -- chip select for cpld active
when "0010" => lpb <= d; -- latch cpld data
when "0011" => cpld_cs <= '1'; -- chip select inactive
when "0100" => a <= "10"; -- address = 01 => led's
cpld_rw <= '0'; -- write to cpld
when "0101" => cpld_cs <= '0'; -- generate chip select pulse
when "0110" => cpld_cs <= '1';
when "0111" => a <= "01"; -- address = 01 => Dip switch
when "1000" => cpld_cs <= '0'; -- chip select for cpld active
when "1001" => dipswitch <= d; -- latch cpld data
when "1010" => cpld_cs <= '1'; -- chip select inactive
when others => cpld_cs <= '1';
end case;
process (lled,cpld_rw)
if (cpld_rw='0') then d <= lled;
else d <= "ZZZZZZZZ";

8. This part was taken from Trenz electronic example
process(clk, rst) -- LCD sub-clocks sequencer
begin
if rst= '1' then
idx <= 0;
elsif rising_edge(clk) then
if idx= 3 then idx<= 0; else idx<= idx + 1; end if;
end if;
end process;
process(clk, rst) -- LCD local control signals generator
cs <= '0';
ext_a <= (others=> '0');
ext_d <= (others=> '0');
case idx is
when 0=> ext_a<= "00" & rs; -- set register address
when 1=> cs <= '1';ext_d<= cmd; -- write data, activate chip select
when 2=> cs <= '0'; -- deactivate chip select
when 3=> null; -- data hold time
end case;
ext_rw<= '0'; always write to LCD
cs_lcd <= cs; chip select for LCD
csn_lcd<= '0'; always write to LCD
This part was taken from
Trenz electronic example
(see the manual HD44780U
Dot Matrix LCD Controller/
Driver for details)

9. Dot Matrix LCD Controller/
process(clk, rst)
begin
if rst= '1' then
cmd <= x"02"; -- clear DDRAM counter, switch off shift
rs <= '1';
reset <= '1'; -- activate LCD initialization from the beginning
cnt <= (others => '0');
elsif rising_edge(clk) then
if idx = 2 then cnt <= cnt + 1;
end if;
if (reset ='0') then -- normal functionality after initialization
case cnt is
when "000000" => cmd <= x"80"; rs <= '0'; -- DDRAM address to the beginning of the first line
when "000001" => cmd <= std_logic_vector(to_unsigned(character'pos(line1(1)), 8)); rs <= '1';
when "000010" => cmd <= std_logic_vector(to_unsigned(character'pos(line1(2)), 8)); rs <= '1';
when "000011" => cmd <= std_logic_vector(to_unsigned(character'pos(line1(3)), 8)); rs <= '1';
when "000100" => cmd <= std_logic_vector(to_unsigned(character'pos(line1(4)), 8)); rs <= '1';
when "000101" => cmd <= std_logic_vector(to_unsigned(character'pos(line1(5)), 8)); rs <= '1';
when "000110" => cmd <= std_logic_vector(to_unsigned(character'pos(line1(6)), 8)); rs <= '1';
when "000111" => cmd <= std_logic_vector(to_unsigned(character'pos(line1(7)), 8)); rs <= '1';
when "001000" => cmd <= std_logic_vector(to_unsigned(character'pos(line1(8)), 8)); rs <= '1';
when "001001" => cmd <= std_logic_vector(to_unsigned(character'pos(line1(9)), 8)); rs <= '1';
when "001010" => cmd <= std_logic_vector(to_unsigned(character'pos(line1(10)), 8)); rs <= '1';
when "001011" => cmd <= std_logic_vector(to_unsigned(character'pos(line1(11)), 8)); rs <= '1';
when "001100" => cmd <= std_logic_vector(to_unsigned(character'pos(line1(12)), 8)); rs <= '1';
when "001101" => cmd <= std_logic_vector(to_unsigned(character'pos(line1(13)), 8)); rs <= '1';
when "001110" => cmd <= std_logic_vector(to_unsigned(character'pos(line1(14)), 8)); rs <= '1';
when "001111" => cmd <= std_logic_vector(to_unsigned(character'pos(line1(15)), 8)); rs <= '1';
when "010000" => cmd <= std_logic_vector(to_unsigned(character'pos(line1(16)), 8)); rs <= '1';
constant line1: string(1 to 16):= "LCD operations :"; strings to display
See the manual HD44780U
Dot Matrix LCD Controller/
Driver for details
LCD operations :
The result of this
sequence is

10. For shift left and right
constant line2: string(1 to 4):= "DEMO";
when "010001" => cmd <= x"C0"; rs <= '0'; -- DDRAM address to the beginning of the second line
when "010-1-"|"0101--" => cmd <= x"20"; rs <= '1';
when "011000" => cmd <= std_logic_vector(to_unsigned(character'pos(line2(1)), 8)); rs <= '1';
when "011001" => cmd <= std_logic_vector(to_unsigned(character'pos(line2(2)), 8)); rs <= '1';
when "011010" => cmd <= std_logic_vector(to_unsigned(character'pos(line2(3)), 8)); rs <= '1';
when "011011" => cmd <= std_logic_vector(to_unsigned(character'pos(line2(4)), 8)); rs <= '1';
when "0111--"|"10000-" => cmd <= x"20"; rs <= '1';
when "100010" => case dipswitch(1 downto 0) is
when "01" => cmd <= x"1C"; rs <= '0'; -- shift display to the right
when "10" => cmd <= x"18"; rs <= '0'; -- shift display to the left
when others => cmd <= x"80"; rs <= '0'; -- display is unchanged
end case;
when others => cmd <= x"80"; rs <= '0';--cnt <= "000000";
else -- initialization of LCD from the beginning
case cnt is -- delay such as from "000000" to "001000" is important for satisfying LCD timing requirements
when "000000" => cmd <= x"38"; rs <= '0'; -- (x"20" Function Set)|(x"10" 8-bit data)|
-- (x"08" two lines)
when "001000" => cmd <= x"0C"; rs <= '0'; (x"08" display control)|(x"04" display on)|
-- (x"00" cursor off - our case; x"02" cursor on)
when "010000" => cmd <= x"06"; rs <= '0'; -- (x"04" entry mode set)|(x"02" increment on)
when "011000" => cmd <= x"01"; rs <= '0'; (x"01" clear display and DDRAM counter)
when "100000" => reset <= '0'; cnt <= "000000"; -- initialization is finished
when others => null;
end if;
end process;
end Behavioral;
DEMO
The result of this
sequence is 1
S0...S7
For shift left and right

11. The result is Shift right LCD operations : LCD operations :
DEMO
LCD operations :
DEMO
LCD operations :
DEMO 1
S0...S7
when "100010" => case dipswitch(1 downto 0) is
when "01" => cmd <= x"1C"; rs <= '0'; -- shift display to the right
when "10" => cmd <= x"18"; rs <= '0'; -- shift display to the left
when others => cmd <= x"80"; rs <= '0'; -- display is unchanged
end case;
Shift right

12. The result is Shift left LCD operations : LCD operations :
DEMO
LCD operations :
DEMO
LCD operations :
DEMO 1
S0...S7
when "100010" => case dipswitch(1 downto 0) is
when "01" => cmd <= x"1C"; rs <= '0'; -- shift display to the right
when "10" => cmd <= x"18"; rs <= '0'; -- shift display to the left
when others => cmd <= x"80"; rs <= '0'; -- display is unchanged
end case;
Shift left

13. NET "clk48in" TNM_NET = "clk48in";
TIMESPEC "TS_clk48in" = PERIOD "clk48in" 48 MHz HIGH 50 %;
NET "clk48in" LOC = "t9";
NET "init" LOC = "p15";
NET "ext_a<2>" LOC = "H15";
NET "ext_a<1>" LOC = "F16";
# beginning of the changes
NET "ext_a<0>" LOC = "H14"; # H14 pin for expansion header
# for 2x16 LCD this pin must be H13
#NET "csn_lcd" LOC ="G14"; # uncomment for 2x16 LCD
NET "cs_lcd" LOC ="A9"; # for 2x16 LCD this pin must be "G13"
# end of changes
NET "ext_d<2>" LOC = "D15";
NET "ext_rw" LOC = "D16";
NET "ext_d<6>" LOC = "F13";
NET "ext_d<4>" LOC = "E14";
NET "ext_d<0>" LOC = "C16";
NET "ext_d<7>" LOC = "G12";
NET "ext_d<5>" LOC = "F12";
NET "ext_d<3>" LOC = "E13";
NET "ext_d<1>" LOC = "D14";
NET "cpld_cs" LOC = "m16";
NET "cpld_rw" LOC = "m15";
NET "a<1>" LOC = "t10"; NET "a<2>" LOC = "m10";
NET "d<0>" LOC = "b16";
NET "d<1>" LOC = "e15";
NET "d<2>" LOC = "f14";
NET "d<3>" LOC = "G15";
NET "d<4>" LOC = "J14";
NET "d<5>" LOC = "L13";
NET "d<6>" LOC = "L16";
NET "d<7>" LOC = "P16";
Expansion
connector

14. Example 2 library IEEE; use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
entity EA_DIP4x20_lcd is
port (
cpld_rw: inout std_logic;
cpld_cs: out std_logic;
a : out std_logic_vector(2 downto 1);
d : inout std_logic_vector(7 downto 0);
clk : in std_logic; -- clock 48 MHz
rst : in std_logic; -- reset
ext_a : out std_logic_vector(2 downto 0); -- LCD control
ext_d : out std_logic_vector(7 downto 0); -- LCD data
ext_rw : out std_logic; -- LCD read/write
cs_lcd : out std_logic; -- LCD chip select active high
csn_lcd : out std_logic -- LCD data direction );
end EA_DIP4x20_lcd;

15. architecture Behavioral of EA_DIP4x20_lcd is
signal state : std_logic_vector(3 downto 0);
signal lled : std_logic_vector(7 downto 0); -- onboard leds (3 downto 0)
signal lpb : std_logic_vector(7 downto 0); -- onboard pushbuttons
signal dipswitch : std_logic_vector(7 downto 0); -- onboard DIP switchers
signal clk : std_logic; -- local clock
signal div : unsigned (16 downto 0); -- local clock divider
signal reset : std_logic; -- lcd reset sequence active
signal cmd : character; -- character for LCD
signal control : std_logic_vector (7 downto 0); -- control data to lcd
signal scroll_dots : std_logic_vector (5 downto 0); -- number of dots for
-- horizontal scrolling
signal rs : std_logic; -- register select bit for lcd
signal idx : integer range 0 to 3; -- sequencer index for lcd timing
signal cs : std_logic; -- chip select for lcd
signal cnt : unsigned (6 downto 0); -- character, command counter
constant line1: string(1 to 16):= "LCD operations :";
constant line2: string(1 to 4):= "DEMO";
begin
process(clk48, rst) -- local clock generator
if rst= '1' then
div <= (others=> '0');
elsif rising_edge(clk48) then
div<= div + 1;
end if;
end process;
clk<= div(div'left);

16. This blue text is included just in order to read dip switchers through
process(clk48, rst)
begin
if rst= '1' then
state<= (others=> '0');
elsif rising_edge(clk48) then
state<= state + 1;
end if;
end process;
cpld_cs <= '1';
case state is
when "0000“ => a <= "00"; -- address = 00 => push buttons
cpld_rw <= '1'; -- read from cpld
when "0001" => cpld_cs <= '0'; -- chip select for cpld active
when "0010" => lpb <= d; -- latch cpld data
when "0011" => cpld_cs <= '1'; -- chip select inactive
when "0100" => a <= "10"; -- address = 01 => led's
cpld_rw <= '0'; -- write to cpld
when "0101" => cpld_cs <= '0'; -- generate chip select pulse
when "0110" => cpld_cs <= '1';
when "0111" => a <= "01"; -- address = 01 => Dip switch
when "1000" => cpld_cs <= '0'; -- chip select for cpld active
when "1001" => dipswitch <= d; -- latch cpld data
when "1010" => cpld_cs <= '1'; -- chip select inactive
when others => cpld_cs <= '1';
end case;
process (lled,cpld_rw)
if (cpld_rw='0') then d <= lled;
else d <= "ZZZZZZZZ";
This blue text is
included just in
order to read dip
switchers through
CPLD (see tutorial
2 for details)

17. This part was taken from Trenz electronic example
process(clk, rst) LCD sub-clocks sequencer
begin
if rst= '1' then
idx <= 0;
elsif rising_edge(clk) then
if idx= 3 then idx<= 0; else idx<= idx + 1; end if;
end if;
end process;
process(clk, rst) -- LCD local control signals generator
cs <= '0';
ext_a <= (others=> '0');
ext_d <= (others=> '0');
case idx is
when 0=> ext_a<= "00" & rs; -- set register adress
when 1=> cs <= '1';
if rs = '1' then ext_d <= std_logic_vector(to_unsigned(character'pos(cmd),8));
else ext_d <= control;
end if; -- write data, activate chip select
when 2=> cs <= '0'; -- deactivate chip select
when 3=> null; -- data hold time
end case;
ext_rw<= '0'; -- always write to LCD
cs_lcd <= cs; -- chip select for LCD
csn_lcd<= '0'; -- always write to LCD
This part was taken from
Trenz electronic example
(see the manual HD44780U
Dot Matrix LCD Controller/
Driver for details)
The only change is shown in green
color. It was done to separate data
to LCD and control signals to LCD

18. The result of this sequence is Line 1;……..End 1 4 lines 20 characters
process(clk, rst)
begin
if rst= '1' then
control <= x"00"; -- clear DDRAM counter, switch off shift
rs <= '1';
reset <= '1'; -- activate LCD initialization from the beginning
cnt <= (others => '0');
scroll_dots <= (others => '0');
elsif rising_edge(clk) then
if idx = 2 then cnt <= cnt + 1;
end if;
if (reset ='0') then -- normal functionality after initialization
case cnt is
when " " => control <= x"80"; rs <= '0'; -- first line
when " " => cmd <= 'L'; rs <= '1';
when " " => cmd <= 'i'; rs <= '1';
when " " => cmd <= 'n'; rs <= '1';
when " " => cmd <= 'e'; rs <= '1';
when " " => cmd <= ' '; rs <= '1';
when " " => cmd <= '1'; rs <= '1';
when " " => cmd <= ';'; rs <= '1';
when " " => cmd <= '.'; rs <= '1';
when " " => cmd <= 'E'; rs <= '1';
when " " => cmd <= 'n'; rs <= '1';
when " " => cmd <= 'd'; rs <= '1';
when " " => cmd <= ' '; rs <= '1';
when " " => cmd <= '1'; rs <= '1';
Line 1;……..End 1
The result of this
sequence is
4 lines
20 characters

19. The result of this sequence is The result of this sequence is
when " " => control <= x"94"; rs <= '0';-- second line
when " " => cmd <= 'L'; rs <= '1';
when " " => cmd <= 'i'; rs <= '1';
when " " => cmd <= 'n'; rs <= '1';
when " " => cmd <= 'e'; rs <= '1';
when " " => cmd <= ' '; rs <= '1';
when " " => cmd <= '2'; rs <= '1';
when " " => cmd <= ';'; rs <= '1';
when " "|" " => cmd <= '.'; rs <= '1';
when " "|" " => cmd <= '#'; rs <= '1';
when " " => control <= x"C0"; rs <= '0'; --third line
when " " => cmd <= 'L'; rs <= '1';
when " " => cmd <= 'i'; rs <= '1';
when " " => cmd <= 'n'; rs <= '1';
when " " => cmd <= 'e'; rs <= '1';
when " " => cmd <= ' '; rs <= '1';
when " " => cmd <= '3'; rs <= '1';
when " " => cmd <= ';'; rs <= '1';
when " "|" "|" " => cmd <= ' '; rs <= '1';
when " " => cmd <= 'E'; rs <= '1';
when " " => cmd <= 'n'; rs <= '1';
when " " => cmd <= 'd'; rs <= '1';
when " " => cmd <= ' '; rs <= '1';
when " " => cmd <= '3'; rs <= '1';
Line 1;……..End 1
The result of this
sequence is
Line 2;…##########
Line 1;……..End 1
The result of this
sequence is
Line 2;…##########
Line 3; End 3

20. the number of dots for scroll
when " " => control <= x"E0"; rs <= '0'; -- forth line
when " " => cmd <= 'L'; rs <= '1';
when " " => cmd <= 'i'; rs <= '1';
when " " => cmd <= 'n'; rs <= '1';
when " " => cmd <= 'e'; rs <= '1';
when " " => cmd <= ' '; rs <= '1';
when " " => cmd <= '4'; rs <= '1';
when " " => cmd <= ';'; rs <= '1';
when " "|" "|" " => cmd <= ' '; rs <= '1';
when " " => cmd <= 'E'; rs <= '1';
when " " => cmd <= 'N'; rs <= '1';
when " " => cmd <= 'D'; rs <= '1';
-- UNCOMMENT one of the following 4 sections
-- sequence of instructions for SHIFT
--when " " => control <= x"3A"; rs <= '0'; -- DH=1: display shift enable
--when " " => control <= x"3D"; rs <= '0'; -- RE=1: extended function set
--when " " => control <= x"1B"; rs <= '0'; -- shift enable for lines 1,2 and 4
--when " " => control <= x"3A"; rs <= '0'; -- RE=0: function set
--when " " => case dipswitch(1 downto 0) is
-- when "01" => control <= x"1C"; rs <= '0'; -- shift display to the right
-- when "10" => control <= x"18"; rs <= '0'; -- shift display to the left
-- when others => control <= x"80"; rs <= '0'; -- display is unchanged
-- end case;
-- sequence of instructions for horizontal SCROLL
----when " " => control <= x"38"; rs <= '0'; -- DH=0: display scroll enable
----when " " => control <= x"3D"; rs <= '0'; -- RE=1: extended function set
----when " " => control <= x"19"; rs <= '0'; scroll_dots <= dipswitch(5 downto 0);
-- scroll enable for lines 1 and 4
----when " " => control <= "10" & scroll_dots; rs <= '0';
----when " " => control <= x"3A"; rs <= '0'; -- RE=0: function set
Line 1;……..End 1
The result of this
sequence is
Line 2;…##########
Line 3; End 3
Line 4; END
DIP switchers 5,4,3,2,1,0 specify
the number of dots for scroll

21. Initialization on reset signal and power on
-- instruction for reverse display
------when " " => control <= x"3B"; rs <= '0'; -- reverse display
-- sequence of instructions for BID mode
when " " => control <= x"3D"; rs <= '0'; -- RE=1: extended function set
when " " => control <= x"07"; rs <= '0'; -- set BID mode
when " " => control <= x"3A"; rs <= '0'; -- RE=0
-- to cansel this sequence set BID bit (less significant bit in the second line) to 0
when others => control <= x"80"; rs <= '0';--cnt <= "000000";
end case;
else -- initialization of LCD from the beginning
case cnt is -- delay such as from "000000" to "001000" is important
-- for satisfying LCD timing requirements
when " " => control <= x"3c"; rs <= '0'; RE=1, 8 bits, 4 lines
when " " => control <= x"09"; rs <= '0'; lines display mode (less significant bit to 1)
when " " => control <= x"38"; rs <= '0'; RE=0
when " " => control <= x"0c"; rs <= '0'; display on, cursor off, cursor blink off
when " " => control <= x"06"; rs <= '0'; -- Entry Mode Set (increment on, display shift off)
when " " => control <= x"01"; rs <= '0'; Display Clear
when " " => reset <= '0'; cnt <= " "; -- initialization is finished
when others => null;
end if;
end process;
end Behavioral;
Initialization on reset
signal and power on

22. There are 2 projects for ISE 5.2 that permit to test the
considered examples
The file shift_LCD.zip includes
project for the example 1
The file shift_LCD20.zip includes
project for the example 2