Data Communications
POINT-TO-POINT CONFIGURATION
Refer to Section 3 for point-to-point configuration instructions.
POINT-TO-POINT PROGRAMMING INFORMATION
This
topic discusses
programming
information of
interest
to someone who is
writing
a
data
communications
driver
or
controller program to communicate
with
this
terminal
in
an
asyn-
chronous point-to-point
environment.
An
asynchronous point-to-point
data
communications
environment
is
characterized
by a flow of
characters
that
have
been
produced over
random
time
intervals.
To
achieve
hardware
synchronization,
each
character
is
delimited
by a ((start
bit"
and
one
or
more ((stop bits".
Character Mode
When
the
terminal
is configured for
Character
mode operation (BLOCK MODE disabled),
the
terminal
sends
characters
to
the
host
computer
as
they
are
entered
through
the
keyboard.
This
mode
of
operation
can
be used for
interactive
or
conversational
exchanges
between
the
terminal
operator
and
an
application program.
Multicharacter Transfers
When
the
terminal
is configured for Block mode operation (Block mode enabled),
data
entered
through
the
keyboard
is
queuedby
the
terminal
and
sent
as
a block
after
the.
key
is
pressed.
If
handshaking
is
disabled,
the
data
block is
sent
when
the.
key
is
pressed. When
the
DCI/DC2/DCI
handshake
is enabled, pressing
the.
key
causes
the
terminal
to
send
a DC2 to
the
host
computer
after
a
DCl
is received
and
then
send
the
data
block
when
the
computer
responds
with
another
DCl.
The
operation of
the.
key
is
described
in
detail
in
Section
9.
There
are
certain
other
functions which always
result
in
a
multicharacter
(block)
data
trans-
fer.
• Terminal-to-computer
data
transfers
initiated
by
an
((Ec&p"
or
((Ec
d"
sequence.
•
User
key-to-computer
data
transfer
C(T"
type).
• Responses to
status
requests
from
the
host computer.
• Responses to
cursor
sensing
requests
from
the
host
computer.
The
driver
program
at
the
host
computer
must
support
whatever
handshaking
process is
configured
at
the
terminal
(no
handshake,
DCl
trigger
handshake,
or
DCI/DC2/DCl
hand-
shake).
In
the
latter
case,
the
DC2
must
be recognized
as
a
request
to
send
data
and
the
DCI
must
be
sent
to
trigger
the
transfer
after
systembuffers
have
been allocated to receive
the
data
block. Additional software
support
may
be needed depending upon
your
need for
terminal
or
device control.
The
I
nhHndShk
(G)
and
I
nhDC2(H)
fields of
the
terminal
configuration
menu
specify which form
of
handshaking
the
terminal
will use.
The
Terminal
Configuration
menu
is
described in Section 3.
7-10
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