How to control a HD44780-based Character-LCD
The Industry Standard Character LCD
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© 1995-2012 Peter Ouwehand.
Last updated on 2012-10-03
General info and code-examples
TOC
1. General
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.
1.2. Usage
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1.3. Purpose
Uuuhm..
2. HD44780-based LCD modules
Data from HITACHI LIQUID CRYSTAL CHARACTER DISPLAY MODULE and OPTREX DOT MATRIX LCD MODULE databooks.
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 2.2., 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 (1stcontroller)
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 (2ndcontroller)
16 n.c.      
2.2. Instruction set
Table 2.3. 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.

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
2.3. Visible DDRAM addresses
2.3.1. 1-line displays
Shown after reset (with N=0).
1-line LCD
Table 2.5. DDRAM address usage for a 1-line LCD
Display size Visible
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).
2.3.2. 2-line displays
Shown after reset (with N=1).
2-line LCD
Table 2.6. DDRAM address usage for a 2-line LCD
Display size Visible
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).
2.3.3. 4-line displays
Shown after reset (with N=1).
4-line LCD
Table 2.7. DDRAM address usage for a 4-line LCD
Display size Visible
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 1st controller and
(00..39) on 2nd controller
(0x00..0x27 + 0x40..0x67) on 1st controller and
(0x00..0x27 + 0x40..0x67) on 2nd 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.
2.4. Interfacing
2.4.1. 8-bit interface
Example of busy flag testing using an 8-bit interface.
8-bit interface
2.4.2. 4-bit interface
Example of busy flag testing using a 4-bit interface.
4-bit interface



Example of data transfer using a 4-bit interface.
4-bit interface
2.5. Character set
Characterset for 5x7 dot font
LCD character set
2.6. Related pages
Private sites:
- Fil's FAQ-Link-In Corner: LCD Technology FAQ
- Fil's FAQ-Link-In Corner: HD44780-based LCD
- Ian Harries: LCD Module to PC Interfacing Example
- Ian Harries: HD44780-based LCD Modules
- Mark Owen: User-defined graphics on HD44780-based LCDs (JavaScript required; Internet Explorer may complain at the quantity of it)

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