J
Serial Pri nter
Your
KAYPRO 10 was
designed
to
be as easy
to
use as possible. The standard
KAYPROexpanded system
consists
of
your
computer
connected
to
a standard
parallel
printer
via the parallel
connector,
and
connected
to
a modem via the
RS-
232C serial connector, J4. However,
if
you have a serial printer, you
will
need
to
adapt
your
serial
interface
for
your
printer.
The
following
information
is provided
to
aid
such
modifications.
Please
note
that
Non-Linear Systems and Kay
Computers
make no guarantees
about
the
suitability
of
a given serial
printer
for
use
with
the KAYPRO 10 RS-232C serial in-
terface. The reasons
for
some
of
the
difficulties
are given here, but before you
purchase
any serial printer,
insist
upon a
demonstration
of
its
operation.
There are three
things
you
must
do
if
you are
to
use a serial
printer
with
the
KAYPRO
10
computer:
1.
You
must
tell
CP/M
to
redirect
the
printer
output
to
the
serial interface. Use
STAT
to change the
physical
assignment,
like this: A>STAT LST: = TTY:
2.
You
can make the change
from
a parallel
printer
(LPT:)
to
serial (TTY:) perma-
nent
for
some
of
your
programs
by using the CON FIG program,
which
is a
part
of
CP/M.
3.
Make sure
that
the line being used by
your
computer
for
data
transmission
(pin 3
of
connector
J4) is
connected
to
the
printer's
data
reception pin.
This
is usually, but
not
always, pin 3
of
the
printer
connector.
4.
The remaining
task
is
to
take care
of
the hand-shaking signal lines.
You
can
strap the
signals, so
that
they
are
always
true (i.e.,
connect
pins 8 and 5
of
connector
J4
to
pin
6).
The
potential
problem
with
defeating
the handshak-
ing
lines in
this
manner
is
that
you have
to
limit
your baud rate to avoid over-
writing
the
printer's
internal
buffer. For example,
if
you leave the the baud
rate
of
the KAYPRO 10 at 300 baud, your
printer
must
be able
to
print
at
least
30
characters
per second.
If
you have
problems
with
overwriting
the
buffer
in your serial
printer
, you
will
have
to
implement
some
handshaking
to
correct
the problem. The KAYPRO 10
uses
pin
20
DTR
(see
the
following
figure) as an
indicator
of
printer
readiness.
For
proper
hand shaking, the serial
printer
must
produce a
"not
busy"
signal
for
pin
5
that
is high when
the
printer
can
accept
data.
Details
of
the
handshaking
required by your
printer
should
be in
its
owner's
manual.
78
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