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DIDS -4 02 -2AM 13
c.
The buffer registers eITlpty during the transITlit ITlode (FraITle Reset
at End of TransITlit option)
d.
An ETX code is detectedln the CE register when either CONTROL
key is not depressed.
(Optional and used to fraITle reset the cursor
when the One Step TransITlit option is used. )
When the CURSR RESET key is depressed, PB3 clocks A33. 8 high to
enable one input to NAND-gate A46. 6.
During each CTS except F(a)
(i. e., F(a) = high), A46.6 is enabled and a low is inserted into the CE register
at each cursor slot.
This low occurs once per character and thereby erases all
cursor slots, regardless of whether or not the cursor is associated with that
particular character.
Thus when the cursor bit does appear at the output of the
delay line, it is erased by the low applied to the input of AI. 8.
When F(a) goes low (signifying the first character, first line position on the
screen), NAND-gate A47. 6 is enabled and F(a) is entered into the CE register as
the cursor.
SiITlultaneously, the leading edge of
F~)
sets flip-flop A40. 12 to
enable NAND-gate A47.11.
The output of A47.11 clocks A40. 8 high during 2CTS
and on the following 3(CTS+1) a Function COITlplete pulse is generated to reset
the function.
Note that this reset function. is initiated by the trailing edge of
F(a) as opposed to the previously discussed functions which were reset by the
cursor.
When any of
th~
conditions specified in b through d occur, A33.8 goes
high to initiate the cursor-reset function.
These conditions are described in
the following text.
a.
ForITl Feed - When a forITl-feed (FF) control code is detected in D3,
the decoded output is coupled through Al 0.8 to initiate a cursor
reset function.
As already described, FF will not be decoded if the
code was preceded in the message by an ESC code.
b.
End of TransITlit (option) - After a transmit sequence, the cursor
ITlay optionally be stepped to the next character position or set
to the fraITle reset position.
In either case, the end of transITlission
is detected by sensing a buffer register eITlpty condition (i. e., BBI,
BB2 and BB3).
After the last character is transmitted, a pulse which
initiates the cursor reset function is generated.
c.
One-Step TransITlit (option) - When the one-step transITlit option is
used, the cursor is either line reset or fraITle reset before trans-
ITlission is initiated.
NAND-gate A17. 11 is enabled when an ETX
character is entered into the delay line by depressing the END key.
(Note that depressing
'c'
and CONTROL to enter ETX will not
enable the gate.) The low output of A17. 11 is used to either line
reset (D to F) or frame reset
(D
to E) the cursor, depending upon
the wiring option eITlployed.
4-116
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