COMMON COMMAND SET AND DISK OPERATION
A
The first high level command required to interface with a Winchester disk is an ATTACH. An ATTACH initializes the SCSI firmware pointers and internal flags. A RAM work area is used to build the SCSI command descriptor block, messages sent in the
The ATTACH command performs the following to a Winchester disk:
If bit 5 of attribute word is "1" (byte offset $10), The firmware sends a Reserve Device SCSI Command ($16) to the SCSI device.
Reserve Command CDB
| BYTE OFFSET | VALUE | COMMENTS | |
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0 | 16 | Command code | ||
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1 | 00 (Note) | LUN is inserted into bits | ||
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2 | 00 | Reserved | ||
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3 | 00 | Reserved | ||
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4 | 00 | Reserved | ||
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5 | 00 | Control byte: no link, no flag | ||
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NOTE: Third party reservation not supported.
If the controller code (byte offset $12) is $17 (synchronous CCS), and if this is the first ATTACH for this device, the firmware sends an identify message followed by a synchronous data transfer request message and a test unit ready command.
Synchronous Data Transfer Request Message
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| BYTE | VALUE | COMMENTS | |
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| 0 | C0 | Identify with reselection | ||
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| message | |
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