Epson LQ-2550 User Manual - Page 122

Option Single-density Double-density High-speed double-density* Quadruple-density* CRT I Pins m 8 0 8 1 8 2 8 3 a 4 Horizdtiz;;sity 60 120 120 240 80 pi * Adjacent dots cannot be printed in this mode. Column reservation numbers The graphics command requires more than one number to specify how many columns to reserve, since one line may use thousands of columns but the printer does not use numbers larger than 255 in decimal. Therefore, the graphics mode command uses two numbers for reserving columns. To figure nl and n2, divide the total number of columns by 256. The quotient is rr.2; the remainder is nl. Since the command is set up for two numbers, you must supply two even if you need only one. When you need fewer than 256 columns, just make nl the number of columns you are reserving and make n2 a zero. For example, if you wish to send 1632 columns of graphics data, nl should be 96 (the remainder) and rr.2 should be 6 (the quotient) because 1632 = (6 x 256) + 96. The printer interprets the number of bytes determined by nl and rr2 as graphics data, no matter what codes they are. This means that you must be sure to supply enough bytes of graphics data or the printer will stop and wait for more data and will seem to be locked. If, however, you supply too much graphics data, the printer will interpret and print the excess as regular text. Using Software and Graphics 4-17