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@--End of Address (EOA).
Indicates the end of
address and is normally followed by text transmission.
@ sets text-out mode and initiates LR C accumulation
beginning with the following character. @ is recog-
nized as a line-control character only when the line
'control is in control mode or text-in mode. In text-
out mode, @ is treated as a normal data (text)
character.
When the line is in control mode, and
@
is trans-
mitted, the line is placed in lower case. When the
line is in text-in mode, the shift bit of the
@
is
ignored and the case is not changed.
In text-out mode, when any text character has its
shift bit set to one and the immediately preceeding
character had its shift bit set to zero, the line control
will generate and transmit the upshift character and
will set upper case before the text character is
transmitted.
Receive
Line-control characters recognized by the IBM Ter-
minal Control Type I during receive operations
follow.
@--End of Block (EOB). Indicates the end of a
block of text. The next received character will be
the LR C character, which will be matched against
the LRC character accumulated in the 2702/03. With
no LRC error (That is, both LRC characters match),
the command is ended with Channel End and Device
End status. The response (answerback) character,
@
or
®,
should then be transmitted by means of
the Write command.
@--End of Transmission (EOT). Indicates the end
of transmission and sets the line in control mode.
The command is terminated with Channel End, Device
End, and Unit Exception status.
@--End of Address (EOA). Indicates that the
characters following will be text. @ sets text-in
and downshift mode and initiates LRC accumulation.
@
is recognized as a control character only if the
line is in control mode; otherwise, it is a normal
data character and has no control effect.
@
Received as a Negative Response to Polling.
When the line control is in control mode, indicates
that the terminal is not ready to receive data. The
command ends with Channel End, Device End, and
Unit Exception status.
®
received following text
(when line is in text-out mode) indicates an error was
detected, and in this case the command is ended with
Channel End, Device End, and Unit Check status and
the Data Check bit set in the sense field.
If
®
is
received while the line is in text-in mode, this
character is treated as a normal data character and
has no control effect.
6?
Received as a Positive Response to Polling.
Indicates that the polled terminal is ready to receive
data.
(X)
received in reply to text (line in text-out
mode) indicates the text was received without error.
In either case, the command ends with Channel End
and Device End status.
If
(X)
is received while the
line is in text-in mode, it is treated as a normal
data character and has no control effect.
Upshift. The upshift character sets text-in upshift
mode if the line is in text-in downshift mode.
If
the
line is already in either text-in upshift mode, text-
out mode, or control mode, this character has no
effect. In any case, the 2702/03 inhibits transfer of
the upshift character to the
I/o
channel, removing
it from the incoming data stream if the line is in
text-in mode. The upshift character is included in
the accumulated LR C character.
Downshift. The downshift character sets text-in to
the downshift mode if the line is in text-in upshift
mode.
If
the line is already in text-in downshift
mode, text-out mode, or control mode, this down-
shift character has no effect. In any case, the
2702/03 inhibits transfer of the downshift character
to the
I/o
channel, removing it from the incoming
data stream.
If
the line is in text-in mode, the
downshift character is included in the accumulated
LR C character.
Delete. Delete characters are removed from the
incoming data stream and their transfer to the I/O
channel is inhibited by the 2702/03. However, the
delete character is included in the accumulated LR C
character if the line is in text-in mode.
Idle. Idle characters are removed from the incom-
ing data stream and their transfer to the
I/o
channel
is inhibited. However, the idle character is included
in the accumulated LR C character
if
the line is in
text-in mode.
Examples of Use of Special Characters
Figure 2-23 shows the use of special characters in
sample messages
Modes of Operation
The IBM Terminal Control Type I can be set in one
of the following mutually exclusive modes.
Operations
2-41
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