How to control a HD44780-based Character-LCD

(Industry-Standard-Character-LCD)
General info and code-examples

1.1. Pin assignment

The pin assignment shown in Table 1.1. is the industry standard for character LCD-modules with a maximum of 80 characters.
The pin assignment shown in Table 1.2. 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!

Table1.1., 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 1.2., 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.

1.2. Instruction set

Table 1.3. HD44780 instruction set
Instruction	Code										Description	Execution time**
	RS	R/W	DB7	DB6	DB5	DB4	DB3	DB2	DB1	DB0
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.

Table1.4. 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

1.3. Visible DDRAM addresses

1.3.1. 1-line displays

Shown after reset (with N=0).

Table1.5. DDRAM address usage for a 1-line LCD
Display size	Visible
	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

1.3.2. 2-line displays

Shown after reset (with N=1).

Table1.6. DDRAM address usage for a 2-line LCD
Display size	Visible
	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

1.3.3. 4-line displays

Shown after reset (with N=1).

Table 1.7. DDRAM address usage for a 4-line LCD
Display size	Visible
	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

1.4. Interfacing

1.4.1. 8-bit interface

Example of busy flag testing using an 8-bit interface.

1.4.2. 4-bit interface

Example of busy flag testing using a 4-bit interface.

Example of data transfer using a 4-bit interface.

1.5. Characterset for 5x7 dot font