I-Data 5250 ALLY - Manual (Page 164)

AGILE 5250 ALLY User’s Guide and Reference Page A-2
XES Mode
The XES command set used by older Xerox printers allows more
functionality than the SCS command set used by IBM printers. For
example, the XES command set allows overlay forms, APA (All-Points-
Addressable) graphics, special fonts for barcodes or logos, and
downloading of fonts and forms from the host System.
All XES commands consist of printable text. Each command is initiated
with a special character called the UDK (User-Defined Key).
The Xerox printer allows the UDK to be assigned to most printable
characters by sending the command
=UDK=%
, where
%
is the character to
be used as the UDK. The UDK should be assigned only to a character that
will not be printed for the duration of the UDK assignment. Additionally,
the UDK should be assigned only to punctuation characters, not to
alphanumeric characters. After the UDK has been assigned, most XES
commands can be sent to the printer as textual data streams.
Some XES commands require a line ending. When a line ending sequence
is used to terminate an XES command, it is not acted upon in the usual
way, but instead is treated as part of the command. The line ending
terminator requirement of some XES commands can pose some special
problems. XES commands themselves also can cause some formatting
conflicts.
Formatting Conflict Overview
When XES commands are sent to the printer, the host System does not
understand the function of these commands. The host System also may be
sending SCS commands to control the document’s formatting. The
coexistence of these separate and potentially conflicting sources of
formatting information can cause the document’s formatting to be
incorrect. This is known as a formatting conflict.
This type of formatting conflict can be exacerbated, because depending
upon the host System and its operating software, the user may have little or
no control over the SCS codes the System uses to control the printer.
Another type of conflict can occur because several XES commands require
a line ending as part of the command. Most IBM host systems
automatically count the number of lines per page and insert an FF (Form
Feed) character when the end of a page is reached. Because each XES
command that requires a line ending consumes one line in the system’s
count, it may be difficult or impossible to fit the required XES commands
within the number of lines the System considers to be a page.