Hardware Reference
In-Depth Information
Figure 14.3
Predei ned characters of size 7
×
5 available in the LCD controller's ROM.
Character ROM
A total of 192 predei ned characters of size 7
5 (see i gure 14.3) are available in the
LCD controller's character generator ROM (CGROM). The CGROM also contains 32
characters of size 10
×
×
5. When the former are used (hence, with 8
×
5-dot blocks), the
LCD can operate with two lines; when the latter (11
5-dot blocks) are used, only
single-line operation is possible. User-dei ned characters are also allowed, so other
exhibition modes are possible, such as full-height (16
×
×
5-dot) characters.
Initialization by Instructions
An important design consideration is the controller's initialization procedure, which
can be done in two ways: automatically, at power up, or by instructions. The latter
can be used when the power supply conditions for automatic initialization are not
met, or for safety. It consists of the following (adjusted) sequence (always with
R/W
=
'0' and
RS
= '0'; as usual, “−” means “don't care”):
