Read Data Operation - Control Data 1700 Maintenance Manual

(2)
(3 )
(4)
(5)
transferred to the computer. After the transfer, the reader starts
motion automatically, reading the next frame and stopping, etc.
Stop tape motion ifa Lost Data condition exists.
Stop tape motion if the Start FF has been cleared.
disables the second 40 msec time delay (29-A12-3).
Clears the Feed 2 FF (page 31) as soon as the information signal
drops. (Information signal drops when the data holes in the tape
leave the read station.)
When the Feed 2 FF clears, the first 40 msec time delay (29-A12-2) is restarted
if tape is still in motion. Information in the Holding Register is now available
to the computer. If tape is still in motion, the information will have to be
transferred from the Holding Register before the next Feedhole signal appears or
a Lost Data condition will result.
READ DATA OPERATION
When the computer executes an Input instruction to the Paper Tape Reader, a
Read Data signal appears at 3l-A17-ll. If the protect requirements are met and
data is available, a Reply signal is generated at 3l-A16-l6. This Reply is sent
to the computer allowing it to transfer data from the Holding Registers to the
1704 A Register, then to continue with program execution at P
+
1. If the
conditions for a Reply are not met, a Reject is sent to the computer preventing
data transfer to the A Register and causing the program to continue at P
+ ~ +
1.
Assuming normal operation, the Read signal will generate a Reply and clear the
Data Ready FF (page 29). The Reply signal to the computer will cause the Read
signal (3l-A17-ll) to drop. Clearing of the Data Ready FF will set the Clutch
3-5