Star Micronics NP-IO manual Calculating Nl and n2 Umber of col- 1 Then nl is N2 is

(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.
umber of col- 1 Then nl is:				and n2 is:
			I		I
L
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.