(ESC) “*” specifies the graphics mode, the CHR$(O) specifies
normal density. Other densities are described later. Any
number of graphics data may follow; the nl and n2 specify the
number of bytes.
To figure the value of nl and n2, you need to work out how
wide your image will be. Because you are limited to the largest
number that can be sent in one byte (255), the formula to work
out nl and n2 is:
if the number of columns is X,
then nl =X MOD 256, and nZ=INT(X/256)
Table 6-l may make the calculation easier.
Table 6-1
Calculating nl and n2.
L
umber of col- 1 Then nl is: I and n2 is: I
512 to 767 X-
768 to 1023 x-768
t
1536 to 1791 X-
1792 to 1920
ml, m2 and so on are specified as before, that is, any desired
combination of pins will be fired by just one number. Because
the top eight pins are used in the dot graphics mode, numbers
between 0 and 255 (in other words, one byte) will fire a unique
combination of pins to produce any pattern of dots. Thus ml,
mZ and so on are the data bytes of the command.
To plot large graphics, use graph paper and draw a line every
eight rows. Draw your graphics shape, and then calculate the
values of each vertical column of eight dots; each value becomes
one data byte. When drawing large shapes, the data byte
CHR$(255) (all pins firing, or a solid block of dots) is common.
A line spacing of 8172 inch (using the (ESC) “A” CHR$(n),
where n =8), will ensure that successive rows of dots will join
perfectly.