General description | 5 |
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Initiator I/0 Lines
| Unit | Data recorded in | |
| concentric tracks | ||
| Selection | ||
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| Logic |
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| Head |
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| Selection | Heads |
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| Logic |
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SCSI |
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Controller | Read/Write |
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| Logic |
| Discs |
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| Seek |
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| Logic |
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| Track |
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| Orientation |
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| Logic |
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| Error |
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| Detection |
| Power Supply |
| Logic |
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Figure 2. Drive functional block diagram
After arriving at the data track and selecting a head, the controller locates the portion of the track where the data is to be read or written. This is called track orientation. Signals from the drive indicate the beginning of each track. The controller uses these signals to determine the position of the head on the track.
When the head is above the desired track location, the controller commands the drive to actually read or write the data. During a read operation, the drive retrieves data from the discs, processes it, and transmits it to the controller. During a write operation, the drive receives data from the controller, processes it, and stores it on the discs.
The drive can also recognize certain errors that may occur during its operation. When an error is detected, it is indicated to the initiator by the SCSI controller.
