Table of Contents
Advertisement
The printer accepts and stores input character data
in
an input
buffer until either the buffer
is
filled
or a
carriage return
(CR)
control
code
is
received.
If the
buffer
is
filled
or a
CR code
is
received, the
content of
the input buffer
is
printed.
Printing of
the
characters
is
achieved by energizing solenoids
in the
print head which drive circular pins
against the ribbon, paper, and platen
as the
print head
is
moved by
the
carriage drive motor forming the characters
in a 7x7
dot-matrix pattern.
Upon
completion of printing the print head
is
moved to
the left
margin and
the
paper
is
advanced one line by energizing the line feed solenoid.
Line feed
(LF)
control codes received by the printer control paper
movement.
Each line feed code received causes the paper to
be
advanced one
line.
The printer has
a
special line feed buffer, separate from the input
buffer, which can store up to 255 line feed commands.
LF control codes
are
received at
the same
data transfer rate
as
character data
(up
to 9300
char-
acters per second)
.
The initial LF code causes an immediate advance of one
line.
Additional line feed codes received are stored
as a
count
in
the line
feed buffer.
Line feed codes and character data sent
to the
printer may be
intermixed, however, all line feeds received are performed before printing the
next line of data.
Automatic line feed upon completion of printing each line may be
disabled
by setting
Section
1
of DIP switch
3
on the printer logic printer
circuit board to
the
OFF position.
If this
function
is
disabled, the first
line of data will be
printed when
a
CR
control code
is
received
or
a
buffer
full condition occurs.
After printing the first line of data, the print head
is
returned to the left margin and the paper
is
not advanced.
The second line
(and
subsequent
lines) of
data must have
at least one LF
control code preceed
each
CR control code
or
buffer full condition, or overprinting will occur.
Line feed codes may be used for limited paper handling functions.
Each line feed code moves
the
paper one-sixth of an
inch.
Thus, for example,
if it is
desired to move
the paper
12
inches, 72 line feed codes are required
before
a
CR
control code
is
sent.
On power-up or reset, the printer
is
preset
to the
10
cpi character
density.
To select
the
condensed
16.7 cpi
character density,
an ESC, DC4 code
sequence
is
sent to the printer.
The input buffer
is
set a 80 characters,
buffer
full, for
10
cpi and
132
characters, buffer
full, for 16.7 cpi.
The
ESC, DC4 code sequence sent
within
a
line of data
is
ignored.
The
16.7
cpi
condensed print
is
deselected by sending an
ESC, DC3
code sequence
or at the
end of
a
print
line.
The two character densities,
10
and 16.7 cpi may be elongated anywhere
in the line.
Elongated characters are double width characters formed by
printing each column of dots within each character twice.
Spaces between
characters are also twice
as
wide.
This effectively halves
the number
of characters per inch
(cpi)
.
Figure 3-2 shows the normal and elongated
character styles.
Elongated characters are initiated by using
the
escape code
ESC,
SO
code sequence
(or
data bit
8
logically
high) and
terminated by the escape code
ESC, SI code sequence
(or
data bit
8
logically
low)
.
Elongated characters
are
automatically terminated at
the end of a line.
Reception of
an
ESC SO code
sequence causes all data following the code sequence to
be
printed elongated.
Control code sequence
ESC, SI
causes all data following the code sequence
to
be
printed normal
size.
Elongated characters may
be initiated and
terminated
any number of times within
a line.
The end of
a
print line terminates
printing of elongated characters, and unless elongated characters are initiated
by the
ESC,
SO code sequence preceeding
the
data
for the
next line, the
characters
in the
next line will be printed normal size.
3-2
Advertisement
Table of Contents
