first LCDs were composed of only the LCD panel. This left the drive
circuitry to the customer. More recent developments have combined
the LCD panel with a PCB( printed circuit board) containing the
drive LSI. This is known as an LCD module, which offers customers
a more complete solution. There are two types of LCD modules: character
and graphic. The character module is composed of 1 to 4 lines of
16 to 40 character blocks having 5 x 7 dots plus cursor. Each character
block is addressed separately and can form alphanumeric characters
and a limited number of symbols. Graphic modules provide users with
a greater degree of flexibility. They are composed of pixels arranged
in rows and columns. Each pixel can be addressed individually for
text, graphics or any combination of the two. An LCD controller
IC (intergrated circuit) is required to operate the graphic LCD.
Some models feature the controller chip built into the module. See
the Graphic Module Section for details. Tecdis dot matrix character
LCD modules are offered in a variety of sizes and configurations.
Character modules are organized in blocks of 5 x 7 dots. This allows
them to display characters to 4 lines of 40 characters. Each model
is STN (FSTN) fluid for enhanced viewing characteristics. Standard
TN fluid is available, but is not recommended for new designs due
to its limited contrast and viewing angle. EL or LED backlighting
is an option for most models. Character modules contain a built-in
HD44780 controller chip that allows the LCD module to receive data
directly from a 4-bit or 8-bit microprocessor or microcontroller.
The HD44780 has 192 character patterns in the character generator
(CG) ROM. Also available is user-definable CG RAM, which allows
the user to program up to 8 characters.