COURIER HIGH SPEED MODEMS
NOTE: You
may
have
to set
your
software
as
well
to
either
hardware
or
software
flow control.
Some
programs
also
require
-
-
that
you
turn
off
the
type
you
are
not
using. -
&HO
Transmit
Data
flow control disabled. Default.
&H1
Hardware
flow control.
Recommended
setting. Requires -
that
your
DTE
and
software
support
Clear
to
Send
(CTS)
at
the
RS-232 interface.
&H2 Software flow control. Requires
that
your
software
support
XON
/XOFF
signaling. See
the
guidelines
that
follow. The ASCII characters
may
be
user-defined. See
Registers S22
and
S23
in
Appendix
B.
That
appendix
also
includes
an
ASCII chart.
&H3 Use
both
hardware
and
software
flow control.
If
you
are
unsure
about
what
your
equipment
supports,
select this
option. But
keep
the
warning,
above,
in
mind
about
software
flow control.
WARNING:
If
possible,
always
use
hardware
flow control. You
may
lose
data
if XON
/XOFF
characters
occur
in
the
data
stream
from
other
sources.
They
may,
for
example,
come
from
the
remote
system:
an
XON from
the
remote
system,
after
your
modem
has
sent
an
XOFF,
can
result
in
buffer
overflow.
Ctrl-S (XOFF)
and
Ctrl-Q (XON) characters also
occur
in
binary
files,
and
are
used
by
Xmodem-type
protocols. You risk
having
these characters
misinterpreted
as
modem
flow control charac-
ters
and
dropped
from
the
data
stream.
Guidelines
If
your
terminal
or
software
does
not
support
Clear
to
Send,
use
of
software
flow control
may
prove
satisfactory if
you're
only
transferring text files.
However,
if
you're
transferring non-text (binary) files,
or
using
an
Xmodem-type
protocol, disable flow control
entirely
(&HO).
In
addition,
be
sure
the
modem
is set to
&BO
and
&NO,
so
that
the
DTE
and
link
rates
are
equal.
4-8 Interface Controls
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