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Dot Patterns And Densities
43
Graphics
The ANSI emulation graphics mode provides both horizontal and vertical dot
placement plotting methods. These methods enable the printing of ASCII
characters in their binary code form. Since each character has a unique
pattern of 1’s and 0’s (dots and voids) that make up its binary code, the
correct placement of these binary forms enables you to form larger images.
For clarity in the text, a binary 1 (a printed dot) will be shown as an X and a
binary 0 (empty dot position) will be shown as a 0.
In the graphics mode, only the low order six bits of a seven-bit character are
used (bits 1-6). Looking at an ASCII code chart, the question mark character
(?) is represented by the binary number 0111111 (bit 7 - bit 1). Since only the
first 6 bits are used, a “?” would print six dots on the paper. A lowercase “j” is
represented by 101010 which would print the following:
Horizontal Graphics / Vertical Graphics
0X0X0X0 LSB
LSB MSBX
0
X
0
X MSB
NOTE: When plotting data, the Least Significant Bit (LSB), Bit 1, is printed
first (left or top bit position) and the Most Significant Bit (MSB), Bit 6,
is printed last (right or bottom bit position).
Notice that in the horizontal graphics mode, the characters are printed on a
single horizontal dot row. In vertical graphics mode, the characters are printed
six dots high, a character per dot column.
Using a series of question mark (that prints all dots) characters in a horizontal
graphic produces a one dot high solid line across the paper. The same
character in vertical graphics mode products a six dot high band across the
paper.
Graphs, charts, and pictures can be produced by repeating, omitting, and
mixing characters across a page.
Dot Patterns And Densities
Table 10 lists the dot patterns for each of the ASCII characters. Each ASCII
character represents six dot positions (or dots) and their spacing is dependent
on the density selected. With a density of 60 and 70 DPI, the dots are spaced
1/60 and 1/70 inch apart respectively. At 120 and 140 CPI, each character
represents six dots spaced 1/120 and 1/140 inch apart. At 180 and 210 DPI
densities, the dots are spaced 1/180 and 1/210 inch apart.
The ASCII characters needed to cover all dot/void combinations are listed in
the chart below. Other valid character combinations (although repeat patterns
of the characters in the chart) are hex 09-13 and hex 20-3E.