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23-C06-2l produces an End of Operation Status (Bit 04) while the signal from
23-C06-23 enables generation of an End of Operation Interrupt (17-C13-l7).
The last (10th) code bar monitored generates a Stop command which is twice as
long as any other keyboard line entry.
This Stop command is sent to the printer
which releases the TTY clutch, causing cam rotation to stop.
One cam rotation
requires 100 msec with 9 msec allowed for monitoring each of the first 9 code
bars and 18 msec for the 10th code bar.
When the alock Control FF clears (tIl), a variable time delay is initiated
(19-Z20-4) after which time a 100 nsec pulse is generated which clears the Mech.
Busy FF (page 23).
The delay time on this variable delay is adjusted so that
the set duration of the Mech Busy FF is 100 msec.
From this time on, the com-
puter can initiate a character transfer from the TTY Holding Register to the
1704 A Register.
If this transfer does not occur before the next start pulse
arrives on the keyboard line, a Lost Data Condition will result.
READ DATA OPERATION
When the computer executes an Input instruction and the TTY is selected, a Read
signal appears at l3-B19-26.
If the Data Read FF (page 17) is set and the Write
Mode FF (page 13) is clear, a Read Enable signal is generated which:
'1)
transfers the contents of the Holding Register to the 1704 A Register.
(2)
sends a Reply to the 1704 after a 1 usec delay.
(3)
generates a 100 nsec clearing pulse (page 15) for the Holding Register
(page 21) and the Data Read FF (page 17).
Clearing of the Data Read FF disables the TTY Busy status.
This places the TTY
in the proper condition for another keyboard entry or for a change of mode.
If
another TTY key is pressed ( or a character read on the P. T. Reader), the
2-20
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