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2.
SECTION VII.
TYPES 204B-ll, 204B-12 MAGNETIC TAPE UNITS
To perform a rewind operation to the beginning-of-tape reflective
marker so that the tape unit is cycled-up and ready to perform an
instruction:
a.
Press the BOT button on the tape unit control panel; or
b.
Momentarily place the tape status switch in the TAPE CHANGE
position and then return it to either the PERMIT or PROTECT
position.
In either case ("a" or "b"), the tape rewinds at six
times read/ write speed and continues at this rate until light
is sensed by the reel diameter photocell.
At this point, the
tape decelerates to the normal read/write speed and continues
at this rate until the beginning-of-tape reflective marker is
sensed.
Power and vacuum remain on, and the read/write
head rotates back into position for reading or writing.
Ma-
nipulating the tape status switch in this manner affects the
tape drive in the same way as does a programmed rewind.
Tape Demounting
1.
Set the tape status switch to the TAPE CHANGE position.
The tape is then
rewound onto the supply reel until the beginning-of-tape marker is sensed
(as described above for tape rewinding procedure 1).
2.
When tape movement stops, press the VACUUM OFF button.
Then
manually rotate the supply reel counterclockwise to wind up the re-
maining tape from the take-up reel and the loop chambers.
3.
Remove the supply reel from the reel mount.
Grasp the opposite sides
of the reel with the fingers while pressing firmly with the thumbs against
the reel hub, thus removing the reel.
NOTE: Always leave the tape status switch in the TAPE CHANGE
position
if
no supply reel is mounted.
OPERA TOR CONSIDERA TraNS
Program Addressing an Unassigned Logical Tape
When a running program addresses a logical tape which has not been assigned by the oper-
ator using the TAPE ADDRESS switches, a central processor "stall" condition occurs.
A stall
condition exhibits the following characteristics:
1.
All central processor and peripheral device activity stops;
2.
The RUN indicator remains illuminated; and
3.
The CONTENTS and ADDRESS indicators r'emain constant (i. e., non-fluctuating).
Depending on the operator's familiarity with the run, he may initiate a restart by perform-
ing the following steps:
1.
Press the STOP button.
NOTE:
The sequence register contains the address of the PDT op code
causing the stall condition.
2.
Assign the logical tape address designated in control character C3 of the
7-6
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