Control Data 1700 Reference Manual page 19

60330S00 A
d) File mark/tape mark, or
e) The transport goes to Not Ready during an operation.
6) Write Motion (A10 -7
=
0001) - initiates write motion. A direct or
buffered output must follow for data transfer to occur.
If
the tape is
at load point, the first word is written 3 inches after load point. All
data requests are rejected while the unit is Busy and before End of
Operation status. For a non-stop Write, initiates a Write Motion or
Write File Mark function within 5 ms after End of Operation status/
interrupt.
If Write Motion is selected and no data transfer follows, the con-
troller locks out and terminates the Write Motion function when it is
time to write the first character on tape. Forward drops to the
selected transport and the transport goes Not Busy after 4 ms but no
End of Operation is generated. To recover from this error condition,
a Unit Select or Clear Controller function can be issued to accept
another motion function. An External Master Clear from the 1700
console will also reset End of Operation.
7) Read Motion (A10-7
=
0010) - initiates read motion. A direct or
buffered input must follow for data transfer to occur. If the tape
is at load point, data can be read within 0.5 inch. CDC tape does
not have information this close to the load point, but other formats
do. All data requests are rejected while the unit is Busy and before
End of Operation status. Read motion terminates by absence of data
from the data handler for three frames. If the computer (or con-
ver~er) stops requesting characters, data transfer stops, but the
tape continues to move to the end of the record. For a non -stop
Read, initiate a Read Motion within 4 ms after End of Operation
status/interrupt.
If
a data transfer request is not received by the
controller in time to complete the transfer properly, a lockout pre-
vents further transfers from the block and all subsequent data trans-
fer requests are rejected. When data is read but not accepted by the
computer, the Lost Data status bit is set if Data Request is late
and data overlaps in 0 register.
S) Backspace (A10-7
=
0011) - moves tape backward one record. Back-
space from load point and non-stop backspace and possible.
9) Write File Mark/Tape Mark (A10-7
=
0101) - moves tape forward
approximately 6 inches and writes a 1-character word of 17 S (File
Mark) in a 60S or a 23 S (Tape Mark) in a 609. The normal End of
Operation sequence follows the Tape Mark/File Mark, writing the
longitudinal check character. When the transport is operating in
binary mode, the File Mark registers a parity error.
10) Search File Mark/Tape Mark Forward (0110) - moves tape forward
until a File Mark or Tape Mark is detected; an end of operation is
generated and tape motion stops.
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