7265 Programmer’s Manual 29Copyright © 2004 TallyGenicom Chapter 2 ANSIDot GraphicsDot graphics allows you to print individual dots at any position on the page and thus to printpictures as well as text. When you enter dot graphics, the printer defaults to a dot density of 72dpi horizontally and vertically, and a line spacing of 12 lpi. Exiting from dot graphics returns theprinter to its prior lpi setting. You can also choose a density of 144 dpih x 72 dpiv. The printerpowers up in low density. The density remains as last set until it is changed, or until power isturned off.Each byte of graphics data defines one column of dots that is six dots high. You can think of theleast significant six bits in the byte as controlling the topmost six wires of the print head, with thefirst bit controlling the top wire and the sixth bit controlling the sixth wire down. If you wanted tofire all six wires, then you would send a byte with a decimal value of 63. Byte values of 0 through31 decimal are interpreted as control codes, so you have to add 64 to any graphics data byte lessthan 32 decimal.You would expect to be able to simply add the value 64 decimal to every graphics data byte; inother words, just set the seventh bit. This is risky because some variations within the 3000product family interpret decimal 127, the Delete character, within a graphics sequence. The effectis to delete everything following the last line terminator. The safest course is:byte_val < 32 then byte_val = byte_val + 64WEIGHT WIRE1 1 ! !2 2 ! !4 3 ! !8 4 ! ! ! ! !16 5 ! !32 6 !65 66 68 72 88 40 88 72 68 66 65Figure 2-5 Dot Column Coding
