Propeller Manual

1: Introducing the Propeller Chip
The character pairs are merged row-by-row such that each character's 16 horizontal pixels are
spaced apart and interleaved with their neighbors' so that the even character takes bits 0, 2, 4,
...30, and the odd character takes bits 1, 3, 5, ...31. The leftmost pixels are in the lowest bits,
while the rightmost pixels are in the highest bits, as shown in Figure 1-7. This forms a long (4
bytes) for each row of pixels in the character pair. 32 such longs, building from the
character’s top row down to the bottom, make up the complete merged-pair definition. The
definitions are encoded in this manner so that a cog’s video hardware can handle the merged
longs directly, using color selection to display either the even or the odd character. It also has
the advantage of allowing run-time character pairs (see next paragraph) that are four-color
characters used to draw beveled buttons, lines and focus indicators.
Figure 1-7: Propeller Character Interleaving
Some character codes have inescapable meanings, such as 9 for Tab, 10 for Line Feed, and 13
for Carriage Return. These character codes invoke actions and do not equate to static
character definitions. For this reason, their character definitions have been used for special
four-color characters. These four-color characters are used for drawing 3-D box edges at run
time and are implemented as 16 x 16 pixel cells, as opposed to the normal 16 x 32 pixel cells.
They occupy even-odd character pairs 0-1, 8-9, 10-11, and 12-13. Figure 1-8 shows an
example of a button with 3D beveled edges made from some of these characters.
Figure 1-8: Button
with 3-D Beveled
Edges
The Propeller Tool includes, and uses, the Parallax True Type
®
font which follows the design
of the Propeller Font embedded in the hardware. With this font, and the Propeller Tool, you
Propeller Manual v1.1 · Page 33