Printronix P5000LJ Series, Programmer'S Reference Manual

Page: 58 / 304

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Chapter 2
Configuring the PCL-II Emulation with Control Codes
Notice that for each line channel 3 is selected, this would select a single
space advance. A 1 could be placed in any or all other channels and the VFC
would still be valid since the printer will only look at the channel selected and
advance to the next line that contained a 1 in that channel. For example, if the
printer was on line 2 and channel 7 was selected, the printer would advance
or slew down to line 20 which is the first line where there is a “1” in channel 7.
The next step would be to convert the above VFC definition into the escape
sequence format. The VFC data portion of the escape sequence reverses the
order of the channels. Once reversed, the 16 bits are then divided into two, 8-
bit bytes, with channel 16 being the Most Significant Bit (MSB) of the word
and channel 1 the Least Significant Bit (LSB) of the word. Refer to Table 10.
Since the escape sequence requires the VFC data to be in ASCII format this
binary data must be converted to ASCII. As in our example, many characters
may convert to “unprintable” ASCII characters (below ASCII OCTAL 037).
Refer to the ASCII Symbol Set chart in Appendix A. Entering unprintable data
can be done in several ways:
The easiest and preferred method involves using “dummy” VFC channels to
cause the converted character to become a printable one. For example,
always have bit 7 and bit 15 a “1”, thus adding %100 to the unprintable
character, and eliminating the confusion of entering unprintable data. Do not
“call” the corresponding channel bit 7 or 15 or else improper spacing will
occur.
If the VFC channels that bits 7 and 15 represent must be used, these
unprintable characters must be manipulated for data entry. In most cases, this
can be dealt with by using the DISPLAY FUNCTIONS mode of your terminal.
Type in the “ESC&l[
byte count ]W” followed by the ASCII characters using the
CONTROL key with the corresponding letter. (Since the CONTROL key
subtracts %100 (100 OCTAL) simply add %100 to the “unprintable” character.
For example, 00000101 converts to %5, adding %100 gives you a %105
which is an E, therefore, pressing a CONTROL E gives the desired result.)
If your terminal doesn't have a DISPLAY FUNCTIONS mode, some EDITOR
programs allow entering the OCTAL equivalents. Some editors do not allow
the user to directly enter OCTAL numbers. In this case, a “dummy” character
would be entered as the VFC data. Next, the EDITOR “CHANGE” command
would be used to change the dummy character to the desired ASCII
character. For example, place an “x” as a dummy character in the VFC data
and use the CHANGE command to replace the “x” with an ASCII 01 (SOH
character) by typing “CHANGEQ “x” to ‘01”. This would replace the “x” with
the unprintable ASCII 01; your escape sequence would appear one character
shorter without DISPLAY FUNCTIONS mode turned on.
This could also be accomplished by changing the specific column to the
ASCII character required. It is important to specify the starting and stopping
column or the CHANGE command will act as a column INSERT. For
Note A “1” corresponds to a hole punched in a physical paper tape.