View source for HD44780 Character LCD

An '''HD44780 Character LCD''' is an industry standard [[liquid crystal display|liquid crystal display (LCD)]] display device designed for interfacing with [[wikipedia:embedded system]]s.  These screens are often found in [[wikipedia:copier|copier]]s, [[wikipedia:fax machine|fax machine]]s, [[wikipedia:laser printer|laser printer]]s, industrial test equipment, networking equipment such as [[wikipedia:router|router]]s and [[wikipedia:storage device|storage device]]s, etc.  These are not the kind of screens one would find in a [[wikipedia:cell phone|cell phone]], [[wikipedia:portable television|portable television]], etc.  They are limited to text only, with eight customizable characters.

Character LCDs can come with or without [[wikipedia:backlight|backlight]]s, which may be [[LED]], [[wikipedia:fluorescent|fluorescent]], or [[wikipedia:electroluminescent|electroluminescent]].  

Character LCDs use a standard 14-pin or 16-pin interface if it has a backlight.

== Pinout ==
[[Image:hd44780_pinout.jpg|right|thumb|HD44780 pinout example.]]

#Ground
#VCC (+5V)
#Contrast adjustment
#Register Select (R/S)
#Read/Write (R/W)
#Clock (Enable)
#Bit 0
#Bit 1
#Bit 2
#Bit 3
#Bit 4
#Bit 5
#Bit 6
#Bit 7
#Optional backlight power rail
#Optional backlight power rail

The backlight power rail differs often, the polarity can be different and some screens need an external resistor. Usually the supply voltage is 5V DC.

Character LCDs can operate in 4-bit or 8-bit mode.  In 4 bit mode, pins 7 through 10 are unused and the entire byte is sent to the screen using pins 11 through 14 by sending 4-bits at a time.

== Standard Sizes ==
These screens come in common configurations of 8x1, which is one row of eight characters, 16x2, and 20x4, among others.  The largest commonly manufactured configuration is 40x4 characters, and actually requires two individually addressable HD44780 controllers with expansion chips.

== Font ==
The character generator ROM contains 208 characters in a 5x8 dot matrix, and 32 characters in a 5x10 dot matrix.  

There is a Japanese version of the ROM which includes [[wikipedia:kana|kana]] characters, and a European version which includes Cyrillic and Western European characters.  

The 7-bit [[wikipedia:ASCII|ASCII]] subset for the Japanese version is non-standard: it supplies a Yen symbol where the backslash character is normally found, and left and right arrow symbols in place of tilde and the rub-out character.

== See also ==
[[wikipedia:LCD Smartie|LCD Smartie]] - open source driver for Microsoft Windows

== External links ==
* [http://www.sparkfun.com/datasheets/LCD/HD44780.pdf Hitachi HD44780U (LCD-II) datasheet]

[[Category:Electrical Component Standard]]