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Interfaces between the LVOl and
most
DEC
computers
are
available. The interface between the LVOl and
a
PDP-8/E
or
PDP-8/M
is
designated
LV8;
the interface between the LVOl and
a
PDP-12
is
designated
LV12;
the
interface between the LVOl and
a
PDP-ll
is
designated
LV11. The LV8 and LVll interfaces
are
described
in
this
manual;
LV12
operation
is
identical
to
the LV8 interface
operation.
1.3
FUNCTIONAL DESCRIPTION
(Figure
1-1)
1.3.1
Print Mode
In the
print
mode of
operation,
the LVOl
accepts,
in
parallel,
7-bit ASCII
input
code from the
LV8, LV12,
or
LVll
Controller. Each character received
is
stored
in
a
l32-character
memory
(buffer).
These 132 characters
represent
one
full line of data
on
11-inch wide paper. Once the 132-character
memory is
full,
the LVOl
automatically prints
the
132 characters
on a
line and then
performs
an
automatic
carriage
return.
If less than
a
full line
is
received,
certain
format control codes
(described
in
Table
3-3)
must
be transmitted
to
the LVOl
to
initiate
printing
of that line.
CONTROL,STATUS
PDP- 8/E
OMNIBUS
LV8
mfg/PER
/
PROCESSOR
'
INTERFACE
DATA
PLOTTER
CONTROL,STATUS
PUP-12 0R
POS. r/o BUS
LV12
LVO'
PDP-8/I
,NTERFACE
DATA
PRINTER/
PROCESSOR
PLOTTER
CONTROL,STATUS
POP—11
UNIBUS
LV11
mfg/19%,
PROCESSOR
INTERFACE
DATA
PLOTTER
(SP-0413
Figure
1-1
LVOl Functional Block
Diagram
When
printing
is
to occur,
each ASCII character
must
be decoded and translated
in
the form of horizontal and
vertical dots that
can
produce
a
recognizable image
on
the paper surface. Each character
is
composed
of dots within
a
7 X 9
matrix;
a
total of 63 bits of
binary
information
are
associated with each character.
Read-only
memories
(ROMS)
are
used
to store
this information until needed
by
the
printer.
These bits
are
sequentially applied
to
the
writing points
to
produce
the desired
pattern.
When
a
black dot
is
required,
a
charge
is
placed
on
the paper; when
no
dot
is
required,
no
charge
is
applied
to
the paper. This process, which
is
also known
as
the
raster
scan
method of
writing,
is
similar
to
the
writing
technique
used
in
television and
on
television-like terminals.
1.3.2
Plot Mode
When the
plot
mode of
operation
is
selected,
the LVOl
accepts,
in
parallel,
8-bit data
bytes.
This
binary
information
is
stored
in
a
1024-bit buffer which
represents
a
full
scan
line
on
ll-inch paper. The line
is
automatically printed
when the last
byte (128th)
is
received. The character
generator
used
in
the
print
mode
is
disabled and the
unweighted binary
information
is
transferred
directly
to
the
writing
surface.
Input
bit 08
prints
as
the left-most
writing point
in
the
current
byte
when
viewing
the resultant
printout.
As
an
example, input
bit 08 would
print
as
the
first dot
on a scan
line if
set
in
the first
byte
of data transmitted.
Because of the electrostatic method of
writing,
data
must
be
presented
to
the
plotter
in the form
of
a
bit map of the
desired
graphical
information. This
can
be
accomplished
with
a
basic software
package
which translates
simple
commands
into
the
required binary
data. Unlike pen
plotters, speed
is
not
dependent
on
the
complexity
of the
image
to
be
produced.
For
example,
the LVOl could
produce
an
8-1/
2 inch
long
X 11
inch wide
graph
or
chart
in
10
seconds,
regardless
of
complexity.
This opens
a new
dimension
in
the
use
of
plotting
with
computers,
since pen
plotters
have
always
had
a
severe
limitation
on
speed
due
to
the
necessity
of
writing
every line with
a
single writing
pen.
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