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In compact mode, overprinting is simulated by emitting a carriage-return character at the end of the line. In
expanded mode, overprinting is simulated by merging characters in the buffer before writing them as a single line in
the printer image file. As the second and subsequent lines are output, each new character is compared with its
corresponding character in the buffer. If the character in the buffer is a space, the new character replaces it. If the
new character is a space or is the same as the character in the buffer, the character in the buffer is retained.
Otherwise, the character in the buffer is replaced with a special character representing an overprinted combination.
This character defaults to DEL (octal 177) but may be changed by altering the OVPCHR-register value.
The HP 2607 printer cannot overprint. A request to suppress spacing will result in a single-line paper advance after
printing.
Entering the
SET LPT POWEROFF
command simulates removing power from the line printer. A
SET LPT
POWERON
command restores power to the printer.
4.8.3
Vertical Format Unit
The HP 2607 supports an 8-channel vertical format unit (VFU), and the HP 2613, 2617, and 2618 printers support
12-channel VFUs. A continuous punched paper tape that controls paper spacing is installed in the VFU reader.
The printer may be commanded to advance the paper until a punched hole is detected in a specified VFU channel.
The length of the tape establishes the length of the forms loaded into the printer.
Initially, the standard VFU tape (part number 02607-80024 for the HP 2607 or 02613-80001 for the HP 2613, 2617,
and 2618) is installed. This tape associates commands for channels 1-8 with the following printer actions:
Channel
Printer Advances to the
1
Top of form
2
Bottom of form
3
Next single space
4
Next double space
5
Next triple space
6
Next half-page
7
Next quarter-page
8
Next sixth-page
For the 02613-80001 tape, channel 9 is punched the same as channel 2, and channels 10-12 are uncommitted.
If the device is in diagnostic mode, the appropriate diagnostic VFU tape (02613-80002 for the 2613 and 2617or
02618-80002 for the 2618) is installed. These tapes associate commands for channels 1-8 as above and for
channels 9-12 with the following actions:
Channel
Printer Advances to the
9
Bottom of form
10
Line before the bottom of form
11
Line before the top of form
12
Top of form
Setting the device back to printer mode restores the standard VFU tape.
The simulator supports the use of custom VFU tape images. A custom tape may be installed in place of the
standard tape by issuing the
SET LPT VFU=<filename>
command. Custom tapes must reserve channel 1 for the
top-of-form location, but the other channels may be defined as desired.
