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12-3. Electronic Vertical Format Unit-(EVFU)
The EVFU is a user-programmable vertical format unit similar in principle to the mechanical VFU tape
readers found on older printer. The EVFU can accomodate maximum form lengths of 96 lines. On
power on status, Default form length is 66 or 72 lines. This lengths is determined by the setting of
SWI-4. (See Section 3-9.)
Any forms length may be specified by programming the EVFU, as long as the specified length does
not exceed the maximum lines.
There are three basic steps for loading vertical format data into the printer. For these steps assume
that the printer is to be set up for 66 lines. Use the same technique for any other forms length.
(a) Send the Start Load command to alert the printer that the following data are EVFU commands.
Start Load is the ASCII control character GS (29 Decimal).
(b) Send 66 pairs of bytes, one pair for each line on the form, which indicate which of the six
available channels is to be set for that line. The format of each byte is:
7
6
5
4
3
2
1
0
BYTE 1
X
1
CH6
CH5 CH4 CH3 CH2 CHI
BYTE 2
X
1
X
X
X
X
X
X
X= Not Used
Channell is used for Top of Form (TOF) and Bottom of Form (BOF). A TOF command must
contain a 1 in channel I and a 0 in every other channel. The first pair of bytes entered must
contain the TOF code or the entire format load will be cancelled, and the printer will revert to
the preprogrammed format. Channels 2 through 6 are vertical tab channels and may be con-
figured in any combination desired, as long as channell contains a 0.1 A in both channels 1 and
2 indicates BOF.
After the 66 byte pairs have been entered, a 67th byte pair containing a TOF code must be entered.
If this is not done, the printer reverts to the preprogrammed format. This TOF code effectively re-
presents the top of the next form.
It
must always follow the entry for the last line of the form used
(e.g. if forms are 15 lines long, TOF must be entered in line position 16).
(c)
Immediately following the 67th entry, load the End of Load command, ASCII control character
RS (Record Separator), 30 Decimal.
EVFU Program Example:
A typical EVFU program is shown in the example. As shown, a Form Feed command (ASCII Charac-
ter FF, 12 Decimal) or a tab to channell will advance the form to the next top of form.
A vertical Tab command (ASCII character VT, 11 Decimal) or a tab to channel 2 .will first advance
the form to line 17, then if issued a second time, to line 25. Note that the VT command always
uses channel 2.
Two consecutive tabs to channel 5 will advance forms to line 15, then to line 17.
Two consecutive tabs to channel 4 will advance forms to line 17, then to the top of the next form
(the printer will always stop at top of form if it is reached before the designated tab channel is de-
tected).
In the course of printing, when line 63 is reached, the BOF setting will automatically cause the forms
to advance to the top of the next form.
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