User`s manual
lYon-Processor
Request
(N
PR)
- High
priority
data
transfers
to
the
PDP-II
Processor.
These
are
direct
memory
access type transfers,
and
are
honored
by the
processor
between
bus
cycles
of
an
instruction
execu-
tion.
NPR
data
transfers
can be
made
between
any
two
peripheral
devices
without
the
supervision
of
the
processor. N ormaHy, N
PR
transfers
are
between a
mass
storage
device, such as a disk
and
core
memory.
An
N
PR
device has very fast access
to
the
bus
and
can
transfer
at
high
data
rates
once
it has
control.
The
processor
state
is
not
affected by
the
transfer;
therefore,
the
processor
can
relinquish
control
while
an
instruction
is
in progress. (See
DMA.)
Non- Transparent
Mode
-
Transmission
of
characters
in a defined
character
format,
e.g.,
ASCII
or
EBCDIC,
in which all defined
control
characters
and
control
character
sequences
are
recognized
and
treated
as such.
NS
-
New
Sync.
Parallel Transmisson -
Method
of
information
trans-
fer in which all bits
of
a
character
are
sent simultane-
ously.
Contrast
with serial transmission.
Path - See
Channel.
Polling - A centrally
controlled
method
of
calling a
number
of
points
to
permit
them
to
transmit
information.
Priority
or
Precedence -
Controlled
transmission
of
messages in
order
of
their designated
importance;
e.g.,
urgent
or
routine.
Private
Line
or
Private Wire - A
channel
or
circuit
furnished
to
a subscriber for his exclusive use
(non
dial-up
).
Protocol - A set
of
rules which govern the sequenc-
ing, identification,
and
synchronization
of
data
exchanged between
data
terminals.
RC
- Received
Character.
Reverse Interrupt
(R
VI) - In Binary
Synchronous
Communications,
a
control
character
sequence
(OLE
sequence) sent by a receiving
station
instead
of
ACK
1
or
ACKO
to
request
premature
termination
of
the
transmission in progress.
C-4
RS
- Request
to
Send.
SDLC
-
Synchronous
Data
Link
Control.
A
protocol
for the
transfer
of
data
between
stations
in a
point-to-
point,
multipoint,
or
loop
arrangement,
using syn-
chronous
data
transmission techniques.
Sei::ure
Line
-
Terminating
a transmission line in a
DC
path,
causing a relay element in
the
telephone
switching network
to
trigger
and
complete
the
circuit
between the calling
station
and
the
called
station.
Voice
or
data
is
then inductively
coupled
between the
transmission line
and
the
terminal. Equivalent
to
tak-
ing the
handset
"off
the
hook"
of
a
conventional
tele-
phone
instrument
or
data
set.
Selective Calling -
The
ability
of
a
transmitting
sta-
tion
to
specify which
of
several
stations
on
the
same
line
is
to
receive a message.
Serial
Transmission - A
method
of
information
trans-
fer
in
which the bits composing a
character
are
sent
sequentially.
(Contrast
with parallel transmission.)
Signal-
In
communication
theory, an intentional dis-
turbance
in a
communication
system.
(Contrast
with
noise.)
Silo
- A first-in, first-out
hardware
buffer, such as
the
RC
Silo
and
the
NSR
in the DV
11,
which use
the
3341
Propagable
Register I.C., described in
Appen-
dix
B.
Simplex
Mode
-
Operation
of
a
channel
in
one
direc-
tion only with no capability
of
reversing.
Single-Address
Message
- A message
to
be delivered
to
one
destination
only.
Start
(~r
Heading
(SOH)
- (a.) In Binary
Synchronous
Communications
(BISYNC),
precedes a block
of
heading characters. (b.) In
DDCMP,
signals a
data
message.
Station
-
One
of
the
input
or
output
points
on
a com-
munications
system.
Stl~fr
a
DLE
- Send a
Data
Link Escape
character
just
prior
to
the
character
to
be
transmitted.
STX
-
Start
of
Text.