Testing, Testing; Usable Pins Labelled Uniquely - Epson FX-80 User Manual
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- Operation manual (203 pages) ,
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- Technical service data (51 pages)
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to 8 labelling system leads to total chaos if you need to fire multiple
pins.
For example, suppose that you want to fire the bottom 3 pins (1, 2,
and 3 with a 1 to 8 labelling system). You'd send the printer a 6 (1
+
2
+
3= 6). But the poor printer has no way of knowing whether you
want to fire pin 6 alone or pins 1 and 5 together (1
+
5 = 6), or any
other combination that adds up to 6. See the problem?
By assigning powers of 2 to each pin (1,2,4,8,16,32,64, and 128),
each pattern of pins corresponds to a unique decimal number from 0
through 255. That's right, no duplicates. With this numbering system,
the number 6 represents pins 2 and 4 (since 2
+
4 = 6). There is no
other way to get 6 by adding powers of 2. (Sorry, Horace, subtraction
is not allowed.) Figure 11-3 shows the pins with their unique labelling
numbers.
Exponent
Values
27
2S
2
5
2'
Usable
2"
pins
22
ffi
2'
20
CD
Figure 11·3. Usable pins labelled uniquely.
Testing, testing
Now that you know the values for the pins, how would you fire the
top pin? Why, with LPRINT CHR$(128), of course! And how about
133
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