32 Line Matrix Printer LinePrinter Plus Programmer's Reference

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Chapter 6 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 XL and the Epson FX 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. These codes are described in

Chapters 3 and 4, which cover the Proprinter and Epson emulations,

respectively. 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 (hex 0B). It prints the contents of the print

buffer (if data are in the buffer) and causes paper movement 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.