Epson LX-90 User Manual - Apple IIc 8699 PIC for LX-90 - Page 18

Chap 3-elements Of Dot-matrix Printing And Computer /printer Communications, The Print Head - ribbon

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Chapter 3 Elements of Dot-Matrix Printing and Computer / Printer Communications This chapter is for those of you who want to know something about how your printer works. It's a simple, non-technical explanation of the basics of dot-matrix printing that will help you understand some of the later chapters, particularly the ones on user-defined characters and graphics. The Print Head The LX-90 uses a print head with nine pins or wires mounted vertically. Each time a pin is fired, it strikes the inked ribbon and presses it against the paper to produce a dot. This dot is about l/72nd of an inch in diameter. (The size varies slightly. depending upon the age of the ribbon and the type of paper used.) As the head moves horizontally across the page, these pins are fired time after time in different patterns to produce letters, numbers, symbols, or graphics. For example, to print a pica capital T (shown in Figure 3-l), the head fires the top pin, moves 1/60th of an inch, fires the top pin again, moves 1/60th of an inch, fires the top pin and the six below it at the same time, moves 1/60th of an inch, fires the top pin, moves another 1/60th of an inch, and fires the top pin once more to finish the letter. All this happens in only l/lOOth of a second. Figure 3-7. A capital T 15

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Chapter 3
Elements of Dot-Matrix Printing
and Computer / Printer Communications
This chapter is for those of you who want to know something about
how your printer works. It’s a simple, non-technical explanation of
the basics of dot-matrix printing
that
will help you understand some
of the later chapters, particularly the ones on user-defined characters
and graphics.
The Print Head
The LX-90 uses a print head with nine pins or wires mounted verti-
cally. Each time a pin is fired, it strikes the inked ribbon and presses it
against the paper to produce a dot. This dot is about l/72nd of an inch
in diameter. (The size varies slightly. depending upon the age of the
ribbon and the type of paper used.) As the head moves horizontally
across the page, these pins are fired time after time in different patterns
to produce letters, numbers, symbols, or graphics.
For example, to print a pica capital T (shown in Figure 3-l), the
head fires
the
top pin, moves 1/60th of an inch, fires
the
top pin again,
moves 1/60th of an inch, fires the top pin and the six below it at the
same time, moves 1/60th of an inch, fires the top pin, moves another
1/60th of an inch, and fires the top pin once more to finish the letter.
All this happens in only l/lOOth of a second.
Figure 3-7. A capital T
15