Epson SQ-2000, Operating Manual

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The SQ-2000 uses the formula n1 + n2 X 256 to determine how
many bytes of graphics data to expect. To determine the values of
n1 and n2, given the number of dot columns of graphics data that
you want to send, use the following formulas (where X is the
number of columns of graphic data):
n1 = X
mod 256
and
n2 = X\256 (where \ represents integer division)
For example, if you wish to send 1632 columns of graphic data,
n1
would be 96 and n2 would be 6 (1632 = 96 + 6
X
256).
When you are using the 24-dot graphics options you must
send three bytes of data for each dot column. Therefore, you refer
to dot columns instead of bytes of graphics data when calculating
nl
and
n2.
(We will explain later how these three bytes are inter-
preted.)
The SQ-2000 will interpret the number of bytes determined by
n1
and
n2
as graphics data, no matter what codes they are. This
means that you must be sure to supply enough bytes of graphic
data, or the SQ-2000 will stop and wait for more data, and will
seem to be locked up. If, on the other hand, you supply too much
graphics data, the excess will be interpreted and printed as regu-
lar text.
Using Hand-Calculated Data to Print Graphics
With what you know now, you can use the simplest applica-
tion of graphics-using hand-calculated data to print graphic
images. While this method is the most tedious of those that we
will explore, it is useful for small graphic elements that are used
many times. Also, it helps you to develop your understanding of
dot graphics.
The first step is to figure out which dots you want to print.
Start by sketching your design on a piece of graph paper as
shown in Figure 6-4. The design in the illustration is only eight
dots high for simplicity, but it could also use multiple print lines.
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