Rewinding
Rewinding is accomplished by giving the rewind order, move tape to load point, MLP. The rewind order starts a unit rewinding and does not tie up the TC. If a motion command is given which calls for a unit that is rewinding, the command is executed, but the action will not take place until the unit is available.
Unit Availability
A unit is unavailable to the program under the following conditions:
- Unit is rewinding.
- Tape is improperly loaded.
- Cover door open.
- Unit overloaded.
- Unit under manual control.
- Power off.
A selected but unavailable unit holds up the TC if a motion order is given for the unit. The TC will be held up until the unit is ready.
| IO Bit | Flag |
| 0 | EOR — End of record |
| 1 | RWF — Read-Write |
| 2 | EOT — End of Tape |
| 3 | Parity |
Connection with High Speed Channel
The high speed channel directs the tape control, and word transfer, just as a program would. A unit is first started reading or writing. The high speed channel is given the memory location of the information, and the number of registers the words read or written will occupy. The channel effects the information transfer. Thus, a high speed channel connected to a tape control handles the programming for the unit word transfers.