Once the equipment has been connected
to
the torrect' port. the baud
rate,
(the speed
of
transmission
of
data)
must be
set
so
that the baud
rates
tor
both the OL and the
connected equipment
are
the
same.
The OL can
be
set
to
operate
at:
75
300
600
1200
2400
4800
9600
19200
(transmit only) baud.
The
OL baud
rate
is
set
by the BAUD command and
IS
set
tor both channels.
The
baud
rates
cannot
be
set
Independently.
The
parity
to
be
used
by
the
OL must
also
be
set
to
match
that
expected
by
the
peripheral
equipment Parity
is
usually used
to
detect Simple transmission errors and may be
set
to
be
even.
odd. mark. space or no
panty.
I.e.
all
8
bits
at
the byte
are
used tor data.
Stop bits mark the end
of
transmiSSion
of
a byte or character
The
OL
will
receive data
with
one.
one and a
half.
or
two
stop
bits,
and
will
always
transmit data with
at
least
two stop
bits.
Note that
If
the OL
IS
set
up
to
9600 baud
It
will
not
receive data with
only one stop bit
at
least
1
'
/2 stop bits
are
required.
It
may
be
necessary
to
connect the handshake lines between the OL and a piece
of
equipment connected
to
it
ThiS
allows the OL and
its
peripheral
to
monitor and control
their
rate
of
communication. They may need
to
do
this
if
one
of
them cannot cope with
the speed
at
which data
is
being transmitted. The OL uses two handshaking lines:
CTS
Clear
to
Send
DTR
Data
Terminal
Ready.
If
the
DTE
cannot cope
With
the
rate
of
transmission
of
data then
it
can negate the
DTR
line which
tells
the
DCE
to
stop sending data. ObViously when the
DTE
has caught up
it
tells
the
DCE,
via the
DTR
line.
to
start transmitting again.
In
the same
way.
the DCE
can stop the
DTE
sending data
by
negating the
CTS
line.
If
additional control Signals
are
required they can be
Wired
up using the
12V
supply available
on
both serial ports.
Although transmission from the QL is often possible without any handshaking
at
all,
the QL will not receive correctly under any circumstances without the use of
CTS
on SERl and
DTR
on SER2.
Communications
on
the OL
are
lull duplex: that
is
both receive and transmit can operate
concurrently.
The parity and handshaking
are
selected when the
senal
channel
is
opened.
command
BAUD
OPEN
CLOSE
function
set
transmission speed
open
senal
channels •
close serial channels
•
•
•
14
see
concept
deVice
tor
a
full
specification
12/84
•
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