Kantronics KPC-4 - Page 24

Flow
Control
Software
Flow
Control
Software
flow
control
sends
special
characters
on
the
TXD
and
RXD
lines
of
the
RS-232
cable.
These
are
the
same
lines
used
for
sending
regular
data
between
the
TNC
and
computer.
Software
flow
control
normally
sends
a
Ctrl-S
to
stop
data
and
a
Ctrl-Q
to
restart
data.
When
a
buffer
gets
close
to
full
the
device
will
send
a
Ctrl-S
and
expect
the
other
device
to
stop.
When
the
buffer
gets
emptier
it
will
send
a
Ctrl-Q
to
tell
the
other
device
to
send
more
data.
How
full
or
empty
a
buffer
is
when
the
special
characters
are
sent
is
determined
by
the
program.
But,
since
the
regular
data
lines
are
being
used
a
Ctrl-S
sent
from
the
keyboard
will
also
stop
data.
And
likewise,
if
there
is
a
Ctrl-S
in
a
file
being
sent,
data
flow
will
stop
until
a
Ctrl-Q
is
received.
XFLOW
needs
to
be
turned
ON
for
the
TNC
to
use
software
flow
control.
XOFF
determines
the
character
sent
by
the
TNC
to
stop
the
flow
of
data
from
the
computer,
and
the
XON
character
restarts
the
flow.
The
TNC
expects
the
computer
to
send
the
STOP
character
to
stop
data
and
the
START
character
to
restart
data.
To
use
software
flow
control
these
commands
would
be
set
as
follows:
XFLOW
ON,
XOFF
$13,
XON
$11,
STOP
$13,
START
$11.
In
the
Transparent
Mode
two
more
commands
are
provided
that
make
it
possible
to
send
or
receive
these
special
characters
and
still
use
software
flow
control.
TXFLOW
controls
flow
control
sent
by
the
TNC
to
the
computer
and
TRFLOW
controls
what
the
TNC
expects
from
the
computer.
If
both
these
commands
are
ON
(and
the
above
commands
are
set
as
stated)
then
software
flow
control
will
take
place
in
both
directions,
to
and
from
the
TNC
and
computer.
But
if
you
are
in
Transparent
Mode
sending
a
file
the
computer
is
not
going
to
be
telling
the
TNC
to
stop
and
start
since
you
are
sending
the
file.
But
if
there
is
a
Ctrl-S
in
the
file,
the
TNC
will
think
the
computer
is
telling
the
TNC
to
stop
and
will
not
send
any
data
to
your
computer
until
it
receives
a
Ctrl-Q
(even
if
you
have
completed
sending
the
file).
To
solve
this
problem
you
can
turn
TRFLOW
OFF
and
send
all
characters
and
turn
TXFLOW
ON
so
the
TNC
will
still
tell
the
computer
when
to
stop
and
restart.
On
the
other
hand,
if
receiving
a
file
set
TRFLOW
ON
and
TXFLOW
OFF.
.
©
Copyright
1989,
Kantronics,
Inc.
All
Rights
Reserved.
Version
2.85
Duplication
of
this
manual
or
the
firmware
without
Operations
Manual
permission
of
Kantronics,
Inc.
is
prohibited.