IBM 5150 - Page 257

I
QC
Establishing a
link
on
a Nonswitched Multipoint
line
QC
1.
The
control
station serializes
the
address
for
the
tributary
or
6.
After
a
short
delay
to
allow
the
control
station
modem
to
receive
~
secondary
station
(AA)
and
sends
its
address
to
the
modem
on
the
the
carrier,
the
tributary
modem
activates
the
'clear
to
send'
'transmitted
data'lineD.
line
II.
~
S.
2. Since
the
'request
to
send'
line and,
therefore,
the
modem
carrier, is
7.
When
station
A
detects
the
active
'clear
to
send'
line,
it
transmits
~
active
continuously
II,
the
modem
immediately
modulates
the
its
response. (For
this
example,
assume
that
station
A has
no
data
:.; ....
carrier
with
the address, and,
thus,
the
address is
transmitted
to
all
to
send;
therefore,
it
transmits
an
EaT
II.)
s·
modems
on the line.
8.
After
transmitting
the
EaT,
station
A
deactivates
the
'request
to
6l
3. All
tributary
modems,
including
the
modem
for
station
A,
send'
line II. This causes
the
modem
to
deactivate
the
carrier and
demodulate
the
address and send
it
to
their
terminals
on
the the
'clear
to
send'
line II.
'received
data'
linell.
9.
When
the
modem
at
the
control
station
(host)
detects
the
absence
4.
Only
station
A responds
to
the
address;
the
other
stations
ignore
of
the
carrier,
it
deactivates
the
'received
line Signal
detector'
the
address and
continue
monitoring
their
'received
data'line.
To
lineEl·
respond
to
the poll,
station
A
activates
its
'request
to
send'
line II,
10.
Tributary
station
A is
now
in receive
mode
waiting
for
the
next
poll
which
causes
the
modem
to
begin
transmitting
a carrier signal.
or
select
transmission
from
the
control
station.
5. The
control
station's
modem
receives
the
carrier and
activates
the
'received line signal
detector'
line
Eland
the
'receiver
signal
element
timing'
line
II
(to send
clock
signals
to
the
control
station).
Some modems
activate
the
clock
signals as soon as
they
are
powered
on.
)
)
)