Epson LQ-2550 User Manual - Page 121

With this numbering system, every combination of the eight pins adds up to a decimal number between 0 and 255, and no numbers are duplicated. Since there are 24 pins in each column, you must make a calculation for each of the three sections in each column. As you can see, this method of planning and printing dot graphics requires considerable calculation. Because triple-density uses 180 columns per inch, printing a single line of triple-density graphics only one inch long requires 540 numbers. Fortunately, commercial software can do the calculations for you. Before you can put these numbers in a graphics program, you need to know the format of the graphics command. The graphics command The graphics mode command is quite different from the other commands used by the printer. For most of the other printer modes, such as emphasized and double-wide, one ESCape code turns the mode on and another turns it off. For graphics, the command is more complicated because the code that turns on a graphics mode also specifies how many columns it will use. After the printer receives this code, it interprets the next numbers as pin patterns and prints them on the paper. Your printer has one command that allows you to use any of the 11 graphics options. The format of the command is: ESC * m n7 n2 data In this command, m selects the graphics option and nl and YL? specify the number of columns to reserve for graphics. The available graphics options are listed in the following table. 4-16 Using Software and Graphics