HP LineJet Printers - PCL-II/LinePrinter Plus Technical Reference Manual, 171249-001PX

Programmable VFC
61
VFC data is the binary data which is loaded into the VFC table in RAM. These
8-bit bytes are sent in the following order following the ESC sequence
terminator: the most significant byte of the first word followed by the least
significant byte of the first word, followed by the most significant byte of the
second word, etc. The most significant bit of each word is channel 16 and the
least significant bit of each word is channel 1.
VFC Data = (MS byte) (LS byte) (MS byte) (LS byte) . . .
(word 1 = line 1) (word 2 = line 2) . . .
Once the VFC has been loaded into the RAM table, the VFC channels are
selected using the ESC&l[0 through 16]V sequence in the same manner as
the standard VFC. The standard and programmable VFC both use the same
table in RAM. Resetting the printer causes the standard VFC to be
recalculated using the current page and text (form) length and a new table to
be overwritten in RAM. The VFC table is also recalculated when the line
spacing, text length, or page length changes.
Special VFC Considerations
Before loading a VFC table, it is recommended that a VFC select of channel 0
be performed. This will bring the printer to the top of the physical page.
When a programmed VFC is loaded into RAM, the logical page length is
automatically calculated using the following formula:
Logical Page Length (in number of lines) =
byte count /2
The example on page 67 shows a VFC table which uses “standard” VFC
definitions and also illustrates a programmable VFC.
Example: Defining a 3.5 inch form at six lines per inch.
1 inch = 6 lines x 3.5 inches = 21 lines
Note If the I/O is configured for 7 bit data, channels 8 and 16
cannot be downloaded with confidence since the eighth bit is
used for the communication protocol. Selecting channels 8
or 16 for 7 bit data is not recommended.