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Section 7: Downloading Characters and Fonts
on. For Letter Quality fonts, the font descriptor byte also identifies the pitch of
the font. If multiple lookup tables have the same combinations of pitch and
quality, only the first one is accessible.
Font Descriptor Byte
Bit 7 1 = This is the default font.
Bit 6 1 = Another lookup table follows.
Bits 5,4 Reserved (should be zero).
Bits 3-0 Quality and pitch.
0000 = Draft
0001 = 10 cpi Letter Quality
0010 = 12 cpi Letter Quality
0011 = Proportional Letter Quality
0100 = Fast Draft
0101 = 10 cpi Enhanced Letter Quality
0110 = 12 cpi Enhanced Letter Quality
0111 = Proportional Enhanced Letter Quality (other values are not
valid).
The pointer, control bytes, and compression masks for the 256 characters make
up an ASCII font (character 0 is first and character 255 is last). The first two
bytes of each entry are the absolute address of the first byte of the character's
image data and are stored high-byte first, then low-byte second.
For examples of the download sequence, see “Designing Monospaced Fast Draft
Characters” on page 125, “Designing Monospaced Draft Characters” on page
130, “Designing Proportionally Spaced Characters” on page 135, or “Designing
Enhanced Letter Quality Characters” on page 141.
Design Considerations
The 24-wire printers use a character matrix that is 24-dots high. The width of the
character matrix can vary. Typical monospaced characters widths are:
Fast Draft 9 dots
Draft 10 dots