during a Read or Inhibit command.
A full duplex communications facility is required
for a terminal to take full advantage of the Type I
Terminal Interrupt feature.
plugged either for Break or for Break (Inhibit
signal on the receive data lead of a full duplex modem
or data set while the 2703 is transmitting to the
terminal. (The receive data lead, a line connecting
the data set to the 2703, provides the input connection
to the 2703 for data signals from the remote termi
nal.) Thus whcn a 'space' signal has been present
during the transmission of two characters, any
transmit-type command (except a Break command)
Interrupt feature, break signals are ignored by the
2703 during transmit break operations. Except for
the Break command, any transmit-type command
ends immediately with
signal on the receive data lead.
receive data leads are not monitored for break
signals during transmit operations.
a Write command, the program may issue a
followed by a Halt
End and Device End status as soon as the line goes
This distinguishes the line break from the non-operational subset
that ends the
Device End, and Unit Check status, and with the Intervention
Required sense bit on.
For all IBM Type I lines, the 2703 accepts a
Break command and transmits a continuous space
signal to the addressed line for a given number of
character times. The length of the space is deter
mined by the number of characters transferred to
the 2703 under the Break command. Because the
2703 ignores bit configuration under a Break
command, any character is
tion. The first character cannot be a pad character
unless the 2703 is at an engineering
307719 or later.
command (except a Break command) on lines under control of
the Type I Terminal Interrupt feature, the receipt of any
characters might be interpreted by the 2703 as a 'break' signal.
This is possible due to the Type I Terminal Interrupt feature's
method of monitoring for a 'break' signal; it monitors for a space
signal on the receive data lead during two consecutive break
sample times. Break-sample times occur just before transmission
of start bits.
The following function pertinent to time-sharing
operations remains unchanged by this feature.
the 2703 recognizes a 'break' signal on the receive
2741 Break Feature
The 2741 Break feature (in conjunction with IBM
Terminal having an Interrupt feature. The 2741
Break feature modifies the terminal-control opera
during a Read, Inhibit, or Prepare command. With
the 2741 Break feature, only
End will be set in this situation, thus allowing
command chaining to occur; (2) The IBM Terminal
from the Western Electric Data
feature is present, the receive-data lead is moni
Write command is ended with
tion Required in the sense byte.
The Break feature in the 2741 is implemented by
the Attention key on the 2741; when pressed, this
key initiates a
multiplexer channel. For the appropriate IBM Line
Adapters or data sets available for use with this
Break feature, refer to the special feature section
in the component description manual, IBM 2741
Communication Terminal, Form GA24-3415.
After getting the Intervention Required during a
Write command, the program may give a Prepare
command followed by a Halt
2703 will present
as soon as the line goes back to Mark. This distin
guishes the line break from the nonoperational