Epson FX-80 User Manual page 311

The FX-80 has three commands that all 7-bit machines can use to
temporarily set the eighth bit. These commands are covered in detail
in Chapter 6 under "Solving the Seven-Bit Dilemma." In brief, the
high-order bit is set with the following command:
LPRINT CHR$ (27)")";
This command converts all codes to the upper range. That works
great as long as you don't need both a high and a low code in the same
command. For example, the command sequence for entering
Graphics Mode requires one number from 0 - 255 and a second num-
ber from 0 - 7. If your application requires the first number to be
greater than 127, you'll have to set the high-order bit before entering
Graphics Mode. But this also makes the second number (and the sub-
sequent graphics data) greater than 127. This sets the graphics width
to some astronomical figure (over 32,OOO). Unfortunately, there is no
way to switch the high-order bit back and forth in the middle of an
ESCape sequence. So 7-bit users are well advised not to use the high-
order bit in Graphics Mode.
Other problems concerning the 7-bit limitation are as follows:
Tabs can't be set in both code ranges.
Width settings are limited when entering Graphics Mode.
The top pin of the print head is unusable in Graphics Mode
(details in Chapter 11).
User-defined characters can't be printed with the top 8 pins (the
standard position for most characters).
Eight pins can't be used in defining characters.
Hex Dump
The hex dump mode echos each code received by the FX-80 onto
the paper as a string of hexadecimal values. You tum hex mode on by
holding the FF button down while you tum the printer on.
The hex dump is useful for determining which codes are creating
problems for a particular system. Some computers change certain
codes when sending them to the printer from BASIC programs. A hex
printout of a program shows exactly what the printer is receiving,
regardless of what the computer is sending (or not sending). The fol-
lowing program lets you see what your computer's problem codes are.
Put the printer in hex dump mode and then RUN this program.
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