Project
Figure 7
have been added to their font spaces ($00-$1F). These
characters are accessed by sending bytes $80-$9F. Please
note, however, that this remapping is only active while in
the Lower 128 mode.
The alternate font is enabled by using code $F3 and
works in a slightly different way. The Upper 128 mode
prints the inverse (black on white) of the Lower 128 mode
characters. In other words, think of the Lower 128 ($F0)
code as normal mode and the Upper 128 ($F1) code as
inverse video mode. The extra graphic characters accessed
using $80-$9F work the same. They appear normal in
Lower 128 mode and inverse in Upper 128 mode.
Commands include six ASCII control characters:
Backspace ($08), Tab ($09), Line Feed ($0A), Form
Feed ($0C), Carriage Return ($0D), and Delete ($7F).
There are four scrolling commands, allowing the entire
display to be moved up ($EC), down ($ED), left
($EE), or right ($EF). Other commands allow the
cursor to be moved up ($E8), down ($E9), left ($EA),
and right ($EB) one space or move HOME ($BA)
without erasing the screen. The cursor can be turned
off ($BB), turned on as an underscore ($BC), turned
on as a block ($BD), set to blink ($BE), and set to not
blink ($BF).
That’s all there is to it. Its rich assortment of
built-in resources and its processing power allow
the ATmega8 microcontroller to make easy work of
generating a text display. Why not try it in your next
project? NV
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NUTS & VOLTS
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Figure 8
Author Bio
Daryl Rictor is an electronics technician with more than 19
years of experience. He currently works as a voice and data
communications specialist. He has an A.S. in Electronics Systems
Technology from the Community College of the Air Force. His
hobbies include single-board computer design, firmware and
software applications development, and experimenting with digital
I/O techniques.
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MAY 2004
