Controlling LCD using BASCOM and AVR

Bascom can handle the two main types of liquid-crystal displays: alphanumeric and graphic. For the time being we will concern ourselves with the most common alphanumeric type. This type of LCD can display characters, numbers and special characters. The most common type of alphanumeric LCD uses a Hitachi HD44780 as display controller. When you are uncertain about what type of display you are holding in your hands, simply look at the chip designations on the back. If one of these says HD44780 you're safe.

Fortunately, the default is set to LCD type 16*2. This is the most common LCD with two lines and 16 characters per line. HD44780 type LCD's have eight datalines, but they can be controlled in a more economical way by using the four 'upper' lines. This saves four i/o pins on your controller. This is the default (4-bit bus mode) in the options window. Sending data in the 4-bit bus mode of course takes two writes for each 8-bits to send. If you really need the LCD to be as fast as possible (and you seldom do) you will have to choose the 8-bit bus mode.

source : qsl.net