Printronix P3000 Series - Manual (Page 81)

5–7 Vertical Format Units
DVFU
The DVFU may be selected in P–Series protocol and is generally used in conjunction with the
Dataproducts interface. A maximum of 12 channels can be assigned to each physical line of a form—
up to 143 lines. A channel number is assigned to each line on the form. The host computer sends chan-
nel codes to the printer, resulting in rapid paper slewing to the next corresponding line. The
programming sequence follows this order: 1) start load code, 2) channel assignments, and 3) end load
code.
The DVFU start load codes are either 6C, 6D, or 6E hex with the PI line high.
Start Load Code – 6C, 6D, or 6E Hex
6E Hex – The DVFU start load code of 6E (hex) with the PI line high initiates the DVFU memory load
routine using the current printer line spacing as the DVFU line spacing.
6C Hex – The DVFU start load code of 6C (hex) with the PI line high initiates the DVFU memory load
routine using 6 lpi as the line spacing, regardless of the current printer line spacing.
6D Hex – The DVFU start load code of 6D (hex) with the PI line high initiates the DVFU memory load
routine using 8 lpi as the line spacing, regardless of the current printer line spacing.
Channel Assignment
Following the start load code, all data bytes received are interpreted as channel assignment data until
the end load code is received. During the channel assignment portion of the load routine, the PI line can
be high or low; if high, however, the channel data cannot be the same as start or end load code data. The
last channel 12 loaded is assigned Bottom–of–Form (BOF). If skip–over perforation is enabled, slew-
ing will occur from the bottom of the form to the top of the form.
A maximum of 12 channels can be assigned to one physical line on the form (multiple channels per line
facilitate the use of a single DVFU load for multiple forms). Two eight–bit data bytes (DVFU charac-
ters) are required per line. As shown in Table 5–4, the least significant six bits of the first data byte are
used to assign channels 1 through 6; the least significant six bits of the second data byte are used to
assign channels 7 through 12. If a bit is set, the corresponding channel is assigned.
Each line on the form requires two bytes. For lines not requiring a channel identification, the two bytes
should not contain channel assignments.
A maximum of 143 lines (286 DVFU bytes) can be assigned on the form. If the printer receives more
than 286 bytes without an end load code, the end load code is “forced” and the load routine is termi-
nated.
CH 1 TOF – The first channel, line 1 of the form, must be assigned channel 1, top–of–form, or the
entire load sequence is ignored and the memory reset. Consequently, when preparing to load the
DVFU memory, position the paper at the required top–of–form position in anticipation of sending the
TOF channel assignment code as the first line loaded. After the memory is loaded, a Form Feed code
(FF, 0C hex) moves the paper to the next channel 1 (top–of–form).
CH 2 VT – Channel 2 is designated as the vertical tab channel. After the memory is loaded, a VT code
(0B hex) moves the paper to the next channel 2. If the printer receives a VT code but channel 2 is not
loaded, the paper advances a single line at the current line spacing.