Control Data 1700 Maintenance Manual page 49

Data FF (page 17) is cleared.
Clearing of the Lost Data FF (page 17) can be done either of two ways:
(1) By any operation which clears the TTY station (M.C., Equipment Clear
or Clear Controller).
(2) By a Select Write Mode function.
If the programmer elects the first method,he will lose the character presently
held in the Holding Register. The second method will not disturb the Holding
Register contents provided data transfer does not take place in the Write Mode.
To continue Read operations from the point where data was actually lost, the
following procedure is recommended:
Keyboard Entry
(1) Release the keyboard by pressing Break Release.
(2) Press Backspace Key two times on keyboard.
(3) Execute clear controller function.
(4) Continue with Read Data operations.
Paper Tape Reader Entry
(1) Release the keyboard by pressing Break Release.
(2) Press Backspace Key three times on keyboard.
(3) Execute Clear Controller Function.
(4) Continue with Read Data operations.
NOTE: During the 180 msec Break condition, the paper tape reader passes
two frames before stopping.
Even with the keyboard locked up, write data operations can be performed after
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