Dot patterns

The LQ-2500 prints graphics the same way that pictures in newspapers and magazines are printed. If you look closely at a newspaper photograph, you can see that it is made up of many small dots. The LQ also forms its images with patterns of dots, as many as 360 dot positions per inch horizontally and 180 dots vertically The images printed by the LQ can, therefore, be as finely detailed as the one on the first page of this chapter.

Eight-pin graphics

The LQ has an eight-pin graphics mode with six densities, so that it is compatible with the many programs written for printers such as the Epson FX and RX series. Although this mode uses only one third of the LQ’s pins, it produces good quality graphics and allows you to use the many programs written for eight-pin graphics.

Twenty-four-pin graphics

The 24-pin graphics mode takes full advantage of the LQ’s print head. It has five densities, but for simplicity this explanation covers only triple-density

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 LQ uses eight-bit bytes of information in its communication with a computer, it needs three bytes of information for each position.

Pin labels

The graphics mode requires a method to tell the printer which pins to fire in each column. The software must send codes for the dot patterns; one number is needed for each column in a line. For each of those columns the print head prints the pattern of dots you have specified.

There are 256 possible combinations of eight pins, so a single number in the range O-255 can be used to specify which of the patterns you want. In this system, one number is assigned to each pin as in Figure 6-1, on the following page.

Graphics and User- defined Characters

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