Control Data 1700 Reference Manual page 20

11) Search File Mark/Tape Mark Backward (0111) - moves tape back-
ward until a File Mark or Tape Mark is detected. When it has been
detected, an end of operation is generated, and tape motion stops.
If no file mark or tape mark is detected, an end of operation will be
generated and motion will stop at load point.
12) Rewind Load (A10-7 = 1000) - rewinds tape at high speed to load
point. The controller remains Busy until tape is positioned at load
point and End of Operation status/interrupt occurs.
13) Rewind Unload (A10-7 = 1100) - rewinds tape to load point. The
tape transport becomes Not Ready upon acceptance of the command.
Manual intervention is required to reload the tape and place the
transport in a Ready condition.
Unit Select: A Unit Select selects a tape transport and its operating condi-
tions or deselects a transport. To perform a Unit Select, load
Q
with W =
DO, E = equipment number, D = 10. Load A according to Figure 7 and
Table 7, and do an Output from A. Tape unit, density, and mode (BCD or
binary) can be selected simultaneously or individually. Unit Select is re-
jected if Controller Active or a program protect fault occurs or if an illegal
code is selected (for example, two densities chosen).
TABLE 7. TAPE UNIT SELECT CODES
BITS 9-7 UNIT SELECT SWITCH
OFA
SETTING
000
0
001 1
010 2
011
3
100 4
101 5
110 6
111
7
1) Character Mode (AD = 1) - In this mode the computer word con-
sists of the lower 6 or 8 bits only.
2) BCD (AI
=
1) - Data is read or written in even parity (608).
3) Binary (A2 = 1) - Data is read or written in odd parity.
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