Epson ActionPrinter 4000 User Manual - Page 102

Graphics closely at a newspaper photograph, you will find that it is made up of thousands of small dots. Your printer also forms its images with patterns of dots, as many as 360 dots per inch, horizontally and 360 dots per inch, vertically. The images printed by this printer can, therefore, be as finely detailed as the ones at the beginning of this section. Twenty-four-pin graphics The graphics mode that takes full advantage of this printer's print head is 24-pin graphics. This mode has five densities, but for simplicity this explanation deals with only one of them, tripledensity. Triple-density prints up to 180 dots per inch, horizontally. As the print head moves across the paper, every 1/180th of an inch it must receive instructions about which of its 24 pins to fire. At each position it can fire any number of pins, from none to 24. This means that the printer must receive 24 bits of information for each column it prints. Since the printer uses 8-bit bytes of information in communicating with the computer, it needs three bytes of information for each position. Pin labels To tell the printer which pins to fire in each column, you first divide each of the vertical columns into three sections of eight pins each and consider each section separately. Since there are 256 possible combinations of the eight pins in each section, you need a numbering system that allows you to use a single number to specify which of the 256 possible patterns you want. This numbering system is shown below: 128 64 32 16 8 4 2 1 Software and Graphics 4-11