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1989-07-13
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EpsJet: An Atari ST software Epson MX-80 emulator for the DeskJet.
Please note: This version (1.0) of EpsJet has had very little
systematic testing. It should be viewed as a beta version. Your inputs
re bugs and missing capabilities are solicited.
COPYRIGHT NOTICE.
EpsJet software and documentation is copyright 1989 by David L.
Bailey. EpsJet may be freely distributed as long as the software and
documentation files are not altered, are kept together, and no charges
(other than nominal media charges) are made for the package.
FILES INCLUDED WITH THIS PACKAGE.
EPSJET.PRG - the MX-80 emulator for the DeskJet
EPSJET.DOC - the file that you are now reading
RESET.PRG - a utility to resynchronize top-of-page (see below)
EPSTOGL.PRG - a utility to toggle emulation off and on
(see below)
WHAT EpsJet DOES.
EpsJet takes output destined for an Epson printer and converts it to a
form that can be properly printed on a Hewlett-Packard DeskJet. Not
all Epson features are implemented, and graphics output will be no
better in resolution than it would be on an Epson MX-80.
Certain application programs may not work properly with EpsJet.
Programs using GDOS output and the FX80.SYS driver should work with
EpsJet to print MX-80-resolution graphics. Text output programs that
request the MX-80 to underscore, print compressed or expanded
characters, print italics, bold, subscripts or superscripts, should
work with EpsJet. Certain other MX-80 functions (for example, tab
settings) are not supported.
EpsJet has many limitations (see below), and should not be viewed as a
proper substitute for a well-designed DeskJet driver for your
applications software.
HOW TO INSTALL EpsJet.
EpsJet is installed by executing ('double-clicking') EPSJET.PRG from
the desktop, or by including EPSJET.PRG in your AUTO folder. There are
no user controls in EpsJet, and therefore no user interface. There is
no provision for 'de-installing' EpsJet; this must be done by
rebooting your computer. EpsJet may not work properly with other
programs (such as printer spoolers) which 'steal' the Trap13 vector.
Please note that while the EPSJET.PRG file is less than 5K bytes, once
installed about 25K of RAM are used; a large buffer area is required
to convert the Epson graphics format to DeskJet graphics format.
KNOWN DEFICIENCIES.
In addition to whatever bugs you may find, EpsJet has the following
design deficiencies:
-Does not implement MX-80 60-dot per inch graphics mode
-Does not implement line spacings other than the standard 6 lines per
inch
-Does not implement MX-80 functions allowing alternate interpretations
of '8th' bit.
-Does not implement unidirectional printing function
-Does not implement perf-skip variations
-Does not implement tab setting function
-Does not implement column width setting function
In addition, certain DeskJet design features, such as the reduced
printable area (top and bottom of page) and the different dot array
(300x300 rather than 120x216), cause some functions to perform in an
unexpected fashion.
-Some text output programs do not use form-feed to indicate start of a
new page, line-spacing to the top of the next page instead. The
DeskJet output will not be satisfactory for these programs.
-Graphics output will start about 1/6 inch down on the page, and the
last 1/2 inch will be missing. The graphics scale will be identical to
that output on an MX-80.
In short, EpsJet is no substitute for a good DeskJet driver for your
applications software.
THE EpsJet PRINTED PAGE
The top 1/6 inch and the bottom 1/2 inch of an 11-inch DeskJet page
are unprintable. EpsJet deals with this situation by starting the
graphics 'top-of-page' at the beginning of the printable area (i. e.,
about 1/6 inch from the top of the paper), printing until it reaches
the lower unprintable area. EpsJet 'swallows' all further graphics
until the 11th inch is reached, or until a form-feed is received.
If a graphics application program defines the end of an 11-inch page
by transmitting a form-feed character, or if it transmits a full 11
inches by spacing properly at the end of the page, all is well except
for the missing 2/3 inch (1/6 + 1/2) at the bottom, and the fact the
printing starts lower on the page (1/6 inch) than it should. The
original scaling is preserved. (Note that the DeskJet scaling function
would have no effect on graphics.)
If a graphics application program does not print a full 11-inch page
(as is the case with a screen dump), there may be positioning problems
with any further graphics output. For example, a second screen dump
would begin immediately after the first, but would be missing a
portion near the bottom of the page before continuing on the following
page. While one could use a DeskJet front-panel form-feed to eject the
first page, EpsJet has no way of knowing that this has happened, and
will still think that it is in the middle of a page. It will then
eliminate about 2/3 inch of graphics from the middle of the following
page.
This problem can be resolved by transmitting the Epson sequence
<Escape @>, which will reset EpsJet to top-of-page and eject any
partially-printed page from the DeskJet. For the convenience(?) of the
user, executing the file RESET.PRG from the desktop will transmit this
sequence.
Printout of text through EpsJet will suffer whatever format problems
would exist printing directly to the DeskJet with DeskJet default
parameters (no scaling, standard page length, etc.). With EpsJet
installed, it is no longer possible (normally) to interpret DeskJet
escape sequences. For the brave, the character sequence
<Escape-Escape> will toggle Epsjet from its emulation mode to a
straight-through mode (i.e., DeskJet escape sequences will work, but
Epson sequences will not); a second <Escape-Escape> will return EpsJet
to the Epson emulation mode. CAUTION: There is no visible indication
of this mode change. When executed from the desktop, the file
EPSTOGL.PRG will transmit the <Escape-Escape> sequence. (Use the
shareware accessory 'JetSet' to set up the DeskJet while in
'straight-through' mode.)
DO NOT use the 'straight-through' mode to print native-mode DeskJet
graphics. It may work some of the time, but eventually <Escape-Escape>
will appear in a sequence of transmitted pixels, switching the
emulator back to the emulation mode. (This problem does not occur in
the emulation mode, since the software is tracking the Epson escape
sequences, and knows to ignore pixel data.)
COMMENTS AND BUG REPORTS
If you find bugs, have comments, would like to see some things done
differently, etc., please let me know. I can be reached (occasionally)
on GENIE as D.BAILEY5. Alternatively, write to me:
David L. Bailey
1100 West Redding Street
Hernando, FL 32642