Epson LX-90 User Manual - Apple IIc 8699 PIC for LX-90 - Page 43

The Print Head and Graphics, this See Appendix D and Problem Codes in Appen

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The Print Head and Graphics Chapter 3 told you a little about how the print head on the LX-90 prints letters: it receives a code for a letter and then fires a pattern of pins to form that letter. In the main graphics mode, however, the LX-90 prints only one column of pins for each code it receives, and it uses only the top eight of the nine pins. Therefore, your graphics program must send codes for dot patterns, one number for each column in a line. For each of those columns the print head prints the pattern of dots you have specified. To print figures taller than eight dots, the print head makes more than one pass. It prints one line, then advances the paper and prints another, just as it does with text. To keep the print head from leaving gaps between the graphics lines as it does between the text lines, the line spacing must be changed to eliminate the space between lines. With a change in line spacing, the LX-90 can print finely detailed graphic images that give no indication that they are made up of separate lines, each no more than 8/72nd of an inch tall. Each pass of the print head prints one piece of the total pattern, which can be as tall or short and as wide or narrow as you desire. You don't have to fill the whole page or even an entire line with your graphics figures. In fact, you can use as little or as much space as you like for a figure and put it anywhere on the page. Note The programs in this chapter do not use the top pin on the print head. In order to use the top pin (which requires data numbers above 127 decimal), you must turn DIP switch 2-2 ON and use the POKE subroutine that is introduced later in this chapter. See Appendix D and "Problem Codes" in Appendix E if you want to use the extra pin. 41

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The Print Head and Graphics
Chapter 3 told you a little about how the print head on the LX-90
prints letters: it receives a code for a letter and then fires a pattern of
pins to form that letter.
In the main graphics mode, however, the LX-90 prints only one
column of pins for each code it receives, and it uses only the top eight
of the nine pins.
Therefore, your graphics program must send codes for dot pat-
terns, one number for each column in a line. For each of those
columns the print head prints the pattern of dots you have specified.
To print figures taller than eight dots, the print head makes more
than one pass. It prints one line, then advances the paper and prints
another, just as it does with text.
To keep the print head from leaving gaps between the graphics lines
as it does between the text lines, the line spacing must be changed to
eliminate the space between lines. With a change in line spacing, the
LX-90 can print finely detailed graphic images that give no indication
that they are made up of separate lines, each no more than 8/72nd of
an inch tall.
Each pass of the print head prints one piece of the total pattern,
which can be as tall or short and as wide or narrow as you desire. You
don’t have to fill the whole page or even an entire line with your
graphics figures. In fact, you can use as little or as much space as you
like for a figure and put it anywhere on the page.
Note
The programs in this chapter do not use the top pin on the
print head. In order to use the top pin (which requires data
numbers above 127 decimal), you must turn DIP switch 2-2
ON and use the POKE subroutine that is introduced later in
this chapter. See Appendix D and “Problem Codes” in Appen-
dix E if you want to use the extra pin.
41