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Processor-to-Terminal
1.
When transmitted, the characters CR, LF,
Space, and Blank must be in the same character
case as the preceding character.
2. The Telegraph Terminal Control Type I auto-
matically inserts the proper shift character in
outgoing data when a change of character case
is encountered.
3. EOA/space must precede the transmission of
text.
Terminal-to-Terminal
1. A Z is the address assigned to the processor and
recognized as such by the Telegraph Terminal
Control Type
I.
2. End of Address (EOA) must precede the trans-
mission of text. EOA for AT&T 83B2 or 83B3
terminals is CR, LF, LTRS. EOA for WU Plan
115A terminals is the space character.
TELEGRAPH TERMINAL CONTROL TYPE II--
OPERATIONS
The Telegraph Terminal Control Type II designed
to service common-carrier TWX Terminals Model
33/35 Type (8-level code, 110 bps only).
Transmission Code
Figure 2-35 shows the transmission code used by the
Telegraph Terminal Control Type II.
The transmission code is the eight-level TWX
code. When transmitting, the terminal control adds
one start bit and two stop bits. When receiving, the
start bit and the stop bits are deleted from the
character and are not sent to the
I/o
channel. Eight
bits are transmitted for each character, but only
seven are classified as data bits; the eighth is the
parity bit.
In
addition, each character has a single-
bit start element and a double-bit stop element. Thus
eleven bits are transmitted for each character.
Example of character U in TWX Transmission Code.
Figure 2-35. TWX Transmjssion Code
2-52
Transmission Code Converted to Interface Code
Figure 2-36 shows the conversion between the TWX
transmission code and the
I/o
interface code.
Special Characters
Figure 2-37 shows the special characters recognized
by the Telegraph Terminal Control Type II.
Receive
During receive operations, the following characters
are recognized by the Telegraph Terminal Control
Type II and cause termination of the
I/o
operation
with subsequent status.
WRU--Who Are You. WRU causes the Channel End
and Device End status to be set.
XON--Transmitter On. XON causes the Channel
End and Device End status to be set.
XOFF--Transmitter Off. XOFF causes the Channel
End and Device End status to be set.
EOT--End of Transmission. EOT causes the Channel
End, Device End, and Unit Exception status to be set.
ACK--Acknowledge. ACK causes the Channel End,
and Device End status to be set.
Delete. The delete character (all Marks) is also
recognized. Transfer of delete characters to the
I/o
channel is inhibited during all read-type opera-
tions.
Transmit
The Telegraph Terminal Control Type II does not
recognize any special characters during transmit-
type operations.
Figure 2-36. Transmission Code Conversion
I/o
Interface Code
TWX Transmission
Code
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