User`s manual
Bit(s)
00
01
02
03
Designation
Receiver Active
Receiver
Resynchronize
Transmitier Go
Transmitter
Underrun
Table
3-11
Line
State
Secondary Register Bit Assignments
Function
Set
to
one
by the Microprocessor when
the
enabled
receiver for
the
associated line has
detected
the
synchronization character(s) for
that
iine. (Receiver
enabling, done via the Line
Control Register,
is
discussed in Paragraph
3.2.2.)
Set
to
one
by
the
PDP-II
program
to
effect
resynchronization during reception
or
to
turn
off
reception on
the
associated line, as described in
Section
3.5.
The Microprocessor searches for the
synchronization character(s) for
the
associated line
if
the receiver for
the
line has been enabled (receiver
enabling is discussed in Paragraph
3.2.2). When the
synchronization character(s)
is
found,
the Micro-
processor sets the Receiver Active bit (Line State
00)
to
one.
If
any characters for
the
associated line are
stored
in
the
RC Silo when this bit
is
set,
they
are
discarded (see Line Progress
07 description).
Set to
one
by
the
PDP-Ii
program
to
command
the
DVII
to
transmit data
on
the associated line. Set
to zero by the Microprocessor whenever
1.
transmitter
principal
and
alternate
byte
counts
are
both
equal
to
zero,
or
2.
transmitter
NXM
(Line State
04)
sets
to
one,
or
3.
transmitter
MPE (Line State
05)
sets
to
one.
This
bit
may be set
to
zero by
the
PDP-II
program
to
abort
transmission.
Set
to
one
by
the
Microprocessor when a character has
been loaded
into
the
transmitter
for the associated
line
and
the
transmitter
has
returned
a Data Not
Available signal.
Should be set
to
zero by the
PDP-II
program
after
it has been read. Indicates
that
one
or
more idling sync characters have been sent by
the
transmitter.
CAUTION
In
byte
count
oriented
protocols
or
trans-
parency
operation
in IBM's BISYNC, idling
of
a sync causes a bad
BCC
and
hence a NAK
from
the
remote
terminal.
Thus,
the
Trans-
mitter
Underrun
bit
indicates
whether
the
NAK
is
the
result
of
line
errors
or
idling syncs.
3-35
Read/Write .
Read
Write
Read
or \v'rite
Read or Write
zero