32 Line Matrix Printer PCL II Programmer's Reference Manual

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Programmable VFC

Programmable VFC allows the user to specify paper movement information

other than the standard VFC definitions shown in Table 7. VFC information is

stored in the memory (RAM) table just as the standard VFC is, only the bytes

of information are loaded into RAM using the following escape sequence:

ESC&l[

byte count

]W[

VFC data

]

The

byte count

parameter specifies the number (in decimal 0 - 255) of VFC

data bytes to expect immediately following the termination of the escape

sequence.

NOTE: An even byte count must be indicated. If an odd byte count is

indicated, the VFC table in RAM will not be overwritten and the data

bytes following the ESC sequence will be read and discarded.

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.

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.

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 35 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