How to control a HD44780-based Character-LCD

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.

Tell me about your applications.
Send a postcard

Uuuhm..

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

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 2.2., 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 for row 0 and 1 (1^stcontroller)
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 for row 2 and 3 (2^ndcontroller)
16	n.c.

*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 F_osc = 250kHz.

*Table 2.4. Bit names*
Bit name	Setting / Status
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

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	0x00..0x07
1*16	00..15	0x00..0x0F [1] [2] [3] [4]
1*20	00..19	0x00..0x13
1*24	00..23	0x00..0x17
1*32	00..31	0x00..0x1F
1*40	00..39	0x00..0x27

[1] Peter Bozzay:
Found DDRAM addresses 0x00..0x07 + 0x40..0x47 to be functional for a 1*16 display size.
Make/model: not mentioned / SC1601AS*B.
[2] Hendrik Abma:
Found DDRAM addresses 0x00..0x07 + 0x40..0x47 to be functional for a 1*16 display size.
Make/model: Samtron / KP-03.
[3] Luigi Candurro:
Found DDRAM addresses 0x00..0x07 + 0x40..0x47 to be functional for a 1*16 display size.
Make/model: Crystal Clear Technology / CMC116-01.
[4] Thierry Giorgetti:
Found DDRAM addresses 0x00..0x07 + 0x40..0x47 to be functional for a 1*16 display size.
Make/model: Xiamen Ocular / GDM1601c (Local copy available as zipped file, approx 278kB).

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	0x00..0x0F + 0x40..0x4F [1]
2*20	00..19	0x00..0x13 + 0x40..0x53
2*24	00..23	0x00..0x17 + 0x40..0x57
2*32	00..31	0x00..0x1F + 0x40..0x5F
2*40	00..39	0x00..0x27 + 0x40..0x67

[1] Author:
According to their datasheets DDRAM addresses 0x80..0x8F + 0xC0..0xCF are used.
Make/model: Emerging Display Technologies / EW162G0YMY (Local copy available as zipped file, approx 85kB).
Make/model: Mitsutech / EW162G0YMY (Local copy available as zipped file, approx 86kB).

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	0x00..0x0F + 0x40..0x4F + 0x14..0x23 + 0x54..0x63 [1] [2]
4*20	00..19	0x00..0x13 + 0x40..0x53 + 0x14..0x27 + 0x54..0x67
4*40	(00..39) on 1^st controller and (00..39) on 2^nd controller	(0x00..0x27 + 0x40..0x67) on 1^st controller and (0x00..0x27 + 0x40..0x67) on 2^nd controller

[1] Rick Mann:
Found DDRAM addresses 0x00..0x0F + 0x40..0x4F + 0x10..0x1F + 0x50..0x5F to be functional for a 4*16 display size.
Make/model: Optrex / DMC16433.
Author:
This matches with the information mentioned in Dmcman_full.pdf paragraph 1.7.6.4. Local copy available as zipped file, approx 176kB.
[2] Tushar Rane:
Found DDRAM addresses 0x00..0x0F + 0x40..0x4F + 0x10..0x1F + 0x50..0x5F to be functional for a 4*16 display size.
Make/model: not mentioned / not mentioned.

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

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

Example of data transfer using a 4-bit interface.

Characterset for 5x7 dot font
LCD character set

Private sites:
- Fil's FAQ-Link-In Corner: LCD Technology FAQ
- Fil's FAQ-Link-In Corner: HD44780-based LCD
- LCD Module to PC Interfacing Example
- HD44780-based LCD Modules

Commercial sites:
- LCD Intro
- HANTRONIX, Inc. Home Page
- Shelly, Inc. - LCD Engineering Application Notes