eXtendo®
Thermal Printer Family
Part No. D-684-124
Mod. No. 4 270919 HW1
page 15 of 33
the sensor when expected, the printer assumes that a paper jam has taken place and
signals this fact via the Status command.
Note
: Care must be taken when mounting the eXtendo printers to insure that the sensor is
not exposed to direct sunlight. The multiple wavelengths of sunlight can cause false
readings from this sensor. Therefore, always shield the chute and sensor from direct
sunlight by the use of chutes, shrouds, covers and similar techniques.
3.7.
Graphic Printing vs. Printing with Printer’s Fonts
One area that causes frequent confusion with regard to printers in general is that of graphic
printing versus printing using the printer’s internal fonts. An explanation here may help clarify this
and make application of the eXtendo® easier for you.
All printers contain a set of commands that will cause the printer to perform different functions (For
the eXtendo® family of thermal printers, these commands are documented in the eXtendo®
Emulation Command Set Reference, p/n D 684 112). The functions are very diverse and there are no
standards for what these functions may be. This allows printer manufacturers to innovate and build
unique features into their products. These commands are often referred to as the printer’s “Native
Commands”.
A printer’s Native Commands are of many different types, but a few are of particular interest to us
here. One is the family of commands for printing graphics. It is these commands that allow pictures
and other graphic images of any type to be printed.
Another family of commands of interest to us here is the text commands. These commands involve
printing text in response to ASCII data sent to the printer. The printer itself contains one or more
character sets. In these character sets, one printable character corresponds to one ASCII character.
There are also commands for positioning and modifying the printout from these character sets,
such as tab and indent commands and commands to enlarge the internal characters by some
factor.
When printing from the internal character sets (we’ll call that “ASCII printing” here for
convenience), characters are sent to the printer and the corresponding characters from the
character set are printed. This has both advantages and disadvantages. The biggest advantage is
that the host need only send one character per printed character. So if 40 characters are being
printed on a line, for example, only 40 bytes of data (plus any overhead for formatting, indenting,
etc.) need be transmitted over the interface. In other words, you can print a lot of text and need
send only a little data. The downside is a lack of flexibility. In today’s Windows® world, we are all
used to printing exactly what we see on our computer screens, in the same font, size, etc. as we see
it. But with ASCII printing, what will be printed will be based on the printer’s internal character set.
The other type of printing we’ll call “Graphic printing”. This is what happens when you print to an
ink jet or laser printer from your PC. The information displayed on the screen is sent to a print
driver. This print driver, which is unique for each printer, translates what is on the screen as a
graphic into graphic Native Commands to be sent to the printer.
Everything printed through a
print driver prints as graphics
. It takes a lot more data to transmit graphics than to transmit ASCII.
In our 40 character example, assuming a 12 x 20 pixel character, the eXtendo® X-80 printer would
require 1,600 bytes (80 bytes/dotline * 20 dotlines) to print one “text” line (please note that these
are estimates, and that various compression routines also impact the amound of data bytes).
The advantage of Graphic printing, then, is the ability to print anything; pictures, text, photos, etc.
exactly as you see it on your screen. The disadvantage is that to do so, much more data must be
sent over the interface.
