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Chapter 3 Proprinter And Epson Vertical Tab Table
VFU Characteristics
Keep in mind the following information when programming and using a VFU:
Elongated Characters. You can use elongated (double high) characters in
VFU programs. The VFU automatically counts one line of elongated
characters as two character lines.
VFU Not Loaded. If the VFU is not loaded, the printer performs a single line
feed in response to VFU commands.
Paper Runaway Protection. If the VFU memory is loaded and a channel
code is sent that was not previously loaded, the printer moves the paper a
single line feed.
Line Spacing. The printer can use either 6 or 8 lines per inch (lpi) spacing.
These VFUs calculate the forms length by line density selected. The 6 and 8
lpi spacing may be mixed on the same form, but should be done carefully.
Form Feed. A form feed sent from the control panel or a command from the
host moves the paper to the first channel 1, which is the top of form.
Vertical Tab. A VT command moves the paper to the next channel 12. If a
channel 12 is not loaded, a line feed will occur.
Proprinter And Epson Vertical Tab Table
The IBM Proprinter III XL and the Epson FX-1050 emulations each contain a
vertical tab table. It is a set of programmed vertical tabs. Various lines of the
form are assigned vertical tabs, which are then accessed by control code for
rapid paper advancement to the tab position.
Two control codes are used for vertical tabbing: ESC B sets single channel
vertical tabs, and VT executes a vertical tab. The Epson emulation also has
ESC / to select one of eight tab channels and ESC b to set the tabs in a
particular channel.
Executing Vertical Tabs
The vertical tab execute code is VT. If there is any data in the print buffer, it is
printed and the paper moves to the next predefined vertical tab position. If a
tab position is not defined, the paper is moved to the next line at the current
line spacing. If a tab position is at the current line, the paper is moved to the
next tab position. If no tab positions are defined between the current line and
the end of the form, the paper moves to the next TOF.
Vertical Tab Positions
Vertical tab positions are set by line number. A maximum of 16 vertical tab
positions can be set on the form. A sample format is shown in Figure 4.
The first vertical tab is set at line 6 for part number data, a second tab is set at
line 8 for part name data, and a third tab is set at line 14 for quantity data. The
ESC B code assigns the vertical tabs to the lines of the form. Once the tab
positions are set, sending the vertical tab execute code (VT) causes the paper