How to control a HD44780-based Character-LCD

(Industry-Standard-Character-LCD)
General info and code-examples
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0. Table Of Contents

1. General

2. HD44780-based LCD modules

3. 8051 example

4. PIC example

5. Miscellaneous examples
- 5.1. PIC16C54 using only 3 lines
- 5.2. .....

6. Manufacturers and Distributors

1. General

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1.1. Disclaimer

THIS DOCUMENT IS PROVIDED TO THE USER ''AS IS''. Etc.etc.

All information in this document is to the best of my knowledge.
The 8051 PL/M51 software is used in applications using 2*16, 2*20, 4*20 and 2*40 LC-Displays.
The PIC ASM software is used in applications using 2*20, 4*20 and 2*40 LC-Displays.
So there should be no risk, but there's still Murphy.

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1.2. Usage

Tell me about your applications.
Send a postcard

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1.3. Purpose

Uuuhm..

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2. HD44780-based LCD modules

Data from HITACHI LIQUID CRYSTAL CHARACTER DISPLAY MODULE and OPTREX DOT MATRIX LCD MODULE databooks.

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2.1. Pin assignment

The pin assignment shown in Table 2.1. is the industry standard for character LCD-modules with a maximum of 80 characters.
The pin assignment shown in Table 2.2. is the industry standard for character LCD-modules with more than 80 characters.

To be sure always check the manufacturers datasheet!
To locate pin 1 on a module check the manufacturers datasheet!

Table 2.1., Pin assignment for <= 80 character displays

Pin number Symbol Level I/O Function

1 Vss - - Power supply (GND)

2 Vcc - - Power supply (+5V)

3 Vee - - Contrast adjust

4 RS 0/1 I 0 = Instruction input
1 = Data input

5 R/W 0/1 I 0 = Write to LCD module
1 = Read from LCD module

6 E 1, 1-->0 I Enable signal

7 DB0 0/1 I/O Data bus line 0 (LSB)

8 DB1 0/1 I/O Data bus line 1

9 DB2 0/1 I/O Data bus line 2

10 DB3 0/1 I/O Data bus line 3

11 DB4 0/1 I/O Data bus line 4

12 DB5 0/1 I/O Data bus line 5

13 DB6 0/1 I/O Data bus line 6

14 DB7 0/1 I/O Data bus line 7 (MSB)

*Table 2.1., Pin assignment for <= 80 character displays*
Pin number	Symbol	Level	I/O	Function
1	Vss	-	-	Power supply (GND)
2	Vcc	-	-	Power supply (+5V)
3	Vee	-	-	Contrast adjust
4	RS	0/1	I	0 = Instruction input 1 = Data input
5	R/W	0/1	I	0 = Write to LCD module 1 = Read from LCD module
6	E	1, 1-->0	I	Enable signal
7	DB0	0/1	I/O	Data bus line 0 (LSB)
8	DB1	0/1	I/O	Data bus line 1
9	DB2	0/1	I/O	Data bus line 2
10	DB3	0/1	I/O	Data bus line 3
11	DB4	0/1	I/O	Data bus line 4
12	DB5	0/1	I/O	Data bus line 5
13	DB6	0/1	I/O	Data bus line 6
14	DB7	0/1	I/O	Data bus line 7 (MSB)

Table 2.2., Pin assignment for > 80 character displays

Pin number Symbol Level I/O Function

1 DB7 0/1 I/O Data bus line 7 (MSB)

2 DB6 0/1 I/O Data bus line 6

3 DB5 0/1 I/O Data bus line 5

4 DB4 0/1 I/O Data bus line 4

5 DB3 0/1 I/O Data bus line 3

6 DB2 0/1 I/O Data bus line 2

7 DB1 0/1 I/O Data bus line 1

8 DB0 0/1 I/O Data bus line 0 (LSB)

9 E1 1, 1->0 I Enable signal row 0 & 1

10 R/W 0/1 I 0 = Write to LCD module
1 = Read from LCD module

11 RS 0/1 I 0 = Instruction input
1 = Data input

12 Vee - - Contrast adjust

13 Vss - - Power supply (GND)

14 Vcc - - Power supply (+5V)

15 E2 1, 1->0 I Enable signal row 2 & 3

16 n.c.

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*Table 2.2., Pin assignment for > 80 character displays*
Pin number	Symbol	Level	I/O	Function
1	DB7	0/1	I/O	Data bus line 7 (MSB)
2	DB6	0/1	I/O	Data bus line 6
3	DB5	0/1	I/O	Data bus line 5
4	DB4	0/1	I/O	Data bus line 4
5	DB3	0/1	I/O	Data bus line 3
6	DB2	0/1	I/O	Data bus line 2
7	DB1	0/1	I/O	Data bus line 1
8	DB0	0/1	I/O	Data bus line 0 (LSB)
9	E1	1, 1->0	I	Enable signal row 0 & 1
10	R/W	0/1	I	0 = Write to LCD module 1 = Read from LCD module
11	RS	0/1	I	0 = Instruction input 1 = Data input
12	Vee	-	-	Contrast adjust
13	Vss	-	-	Power supply (GND)
14	Vcc	-	-	Power supply (+5V)
15	E2	1, 1->0	I	Enable signal row 2 & 3
16	n.c.

2.2. Instruction set

*Table 2.3. HD44780 instruction set*
Instruction	Code										Description	Execution time**
Instruction	RS	R/W	DB7	DB6	DB5	DB4	DB3	DB2	DB1	DB0	Description	Execution time**
Clear display	0	0	0	0	0	0	0	0	0	1	Clears display and returns cursor to the home position (address 0).	1.64mS
Cursor home	0	0	0	0	0	0	0	0	1	*	Returns cursor to home position (address 0). Also returns display being shifted to the original position. DDRAM contents remains unchanged.	1.64mS
Entry mode set	0	0	0	0	0	0	0	1	I/D	S	Sets cursor move direction (I/D), specifies to shift the display (S). These operations are performed during data read/write.	40uS
Display On/Off control	0	0	0	0	0	0	1	D	C	B	Sets On/Off of all display (D), cursor On/Off (C) and blink of cursor position character (B).	40uS
Cursor/display shift	0	0	0	0	0	1	S/C	R/L	*	*	Sets cursor-move or display-shift (S/C), shift direction (R/L). DDRAM contents remains unchanged.	40uS
Function set	0	0	0	0	1	DL	N	F	*	*	Sets interface data length (DL), number of display line (N) and character font(F).	40uS
Set CGRAM address	0	0	0	1	CGRAM address						Sets the CGRAM address. CGRAM data is sent and received after this setting.	40uS
Set DDRAM address	0	0	1	DDRAM address							Sets the DDRAM address. DDRAM data is sent and received after this setting.	40uS
Read busy-flag and address counter	0	1	BF	CGRAM / DDRAM address							Reads Busy-flag (BF) indicating internal operation is being performed and reads CGRAM or DDRAM address counter contents (depending on previous instruction).	0uS
Write to CGRAM or DDRAM	1	0	write data								Writes data to CGRAM or DDRAM.	40uS
Read from CGRAM or DDRAM	1	1	read data								Reads data from CGRAM or DDRAM.	40uS

Remarks:
- DDRAM = Display Data RAM.
- CGRAM = Character Generator RAM.
- DDRAM address corresponds to cursor position.
- * = Don't care.
- ** = Based on Fosc = 250KHz.

Table 2.4. Bit names

Bit name Settings

I/D 0 = Decrement cursor position 1 = Increment cursor position

S 0 = No display shift 1 = Display shift

D 0 = Display off 1 = Display on

C 0 = Cursor off 1 = Cursor on

B 0 = Cursor blink off 1 = Cursor blink on

S/C 0 = Move cursor 1 = Shift display

R/L 0 = Shift left 1 = Shift right

DL 0 = 4-bit interface 1 = 8-bit interface

N 0 = 1/8 or 1/11 Duty (1 line) 1 = 1/16 Duty (2 lines)

F 0 = 5x7 dots 1 = 5x10 dots

BF 0 = Can accept instruction 1 = Internal operation in progress

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*Table 2.4. Bit names*
Bit name	Settings
I/D	0 = Decrement cursor position	1 = Increment cursor position
S	0 = No display shift	1 = Display shift
D	0 = Display off	1 = Display on
C	0 = Cursor off	1 = Cursor on
B	0 = Cursor blink off	1 = Cursor blink on
S/C	0 = Move cursor	1 = Shift display
R/L	0 = Shift left	1 = Shift right
DL	0 = 4-bit interface	1 = 8-bit interface
N	0 = 1/8 or 1/11 Duty (1 line)	1 = 1/16 Duty (2 lines)
F	0 = 5x7 dots	1 = 5x10 dots
BF	0 = Can accept instruction	1 = Internal operation in progress

2.3. Visible DDRAM addresses

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2.3.1. 1-line displays

Shown after reset (with N=0).

*Table 2.5. DDRAM address usage for a 1-line LCD*
Display size	Visible
Display size	Character positions	DDRAM addresses
1*8	00..07	00h..07h
1*16	00..15	00h..0Fh
1*20	00..19	00h..13h
1*24	00..23	00h..17h
1*32	00..31	00h..1Fh
1*40	00..39	00h..27h

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2.3.2. 2-line displays

Shown after reset (with N=1).

*Table 2.6. DDRAM address usage for a 2-line LCD*
Display size	Visible
Display size	Character positions	DDRAM addresses
2*16	00..15	00h..0Fh + 40h..4Fh
2*20	00..19	00h..13h + 40h..53h
2*24	00..23	00h..17h + 40h..57h
2*32	00..31	00h..1Fh + 40h..5Fh
2*40	00..39	00h..27h + 40h..67h

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2.3.3. 4-line displays

Shown after reset (with N=1).

*Table 2.7. DDRAM address usage for a 4-line LCD*
Display size	Visible
Display size	Character positions	DDRAM addresses
4*16	00..15	00h..0Fh + 40h..4Fh + 14h..23h + 54h..63h
4*20	00..19	00h..13h + 40h..53h + 14h..27h + 54h..67h
4*40	(00..39) on 1st controller and (00..39) on 2nd controller	(00h..27h + 40h..67h) on 1st controller and (00h..27h + 40h..67h) on 2nd controller