User`s manual
Table 3-9
Line
Status Register Bit Assignments
Bit
Designation Function
Read/Write
00
LINE
EN
When set
to
1 for the line selected by
bits
0-3
of
the CSR,
Read or Write
(Line Modem Enable)
causes status conditions
DSR, CS, CO, and RING from
the corresponding modem
to
appear in bits
4-7
of
the
LSR and causes status transitions from the same modem
to set the Done bit
(CSR bit 7) to 1 during the scanning
process.
To
set the Line En bit for a line, the line number
is
set in the CSR, then the Line
En
bit is set in the LSR.
Cleared by Initialize and Clear Mux (CSR bit 10).
01
TERM RDY
When set
to
1 for the line selected by bits
0-3
of
the CSR,
Read or Write
(Terminal Ready)
maintains line seizure
("off-hook"
condition) for the corre-
sponding modem.
To
set the TERM RDY bit for a line, the
line number must be in the
CSR, then the TERM RDY bit
is
set in the LSR. Cleared by Initialize and Clear Mux.
02
RS
When set
to
1 for the line selected by bits
0-3
of
the CSR,
Read or Write
(Request
to
Send) conditions
the
corresponding modem
to
transmit data.
To
set the RS bit for a line, the line number must be in the
CSR, then the RS
bit
is
set in the LSR. Cleared by Initialize
and
Clear Mux.
03
NS
When set to 1 for the line selected by bits
0-3
of
the CSR,
Read or Write
(New
Sync) signals the corresponding modem
to
resynchronize on the
(Synchronous
carrier.
To
set the NS bit for a line, the line number must
modem definition) be in the
CSR, then the
NS
bit
is
set in the LSR. Cleared
by Initialize and Clear Mux.
03
SECTX
When set
to
a 1 for the line selected by bits
0-3
of
the CSR,
Read or Write
(Secondary Transmit) signals the corresponding modem
to
transmit on the reverse
( Asynchronous channels.
To
set the SEC TX bit for a line, the line number
modem definition)
must be
in
the CSR, then the SEC TX bit
is
set in the LSR.
Cleared by Initialize and Clear Mux.
04
DSR
Set
to 1 whenever the DSR line from the modem selected
Read only
(Data
Set Ready) by bits
0-3
of
the CSR
is
ON, provided
that
the Line
En
Synchronous
bit for that modem has been set. Indicates the modem
modem definition)
has seized the line.
04
SECRX
Set
to
1 whenever the SEC RX line from the modem Read only
(Secondary Receive)
selected
by
bits
0-3
of
the CSR
is
ON, provided that
(Asynchronous
the Line En
bit
for
that
modem has been set. Indicates
modem definition)
a remote modem
is
signaling the local modem on the
reverse channels.
05
CS
Set to 1 whenever the
CS
line from the modem selected
Read only
(Clear
to
Send)
by bits
0-3
of
the CSR
is
ON, provided that the Line
En bit for the modem has been set. Indicates the modem
is
ready to transmit data. Occurs
in
response to an
RS
(LSR
bit 2).
3-28