7 | SCSI PACKETS |
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Table | SCSI Functions (cont’d) | ||
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SCSI |
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FUNCTION CODE |
| DESCRIPTION | |
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$4C |
| Reserved | |
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$50 |
| Inquiry | |
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$54 |
| Load/Unload | |
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$58 |
| Recover Buffer Data | |
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$5C |
| Request Sense Data | |
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$60 |
| Check Status | |
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$64 |
| Reserve Device | |
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$68 |
| Release Device | |
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$6C |
| New Tape Attach | |
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$70 |
| New Read (disk and tape) | |
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$74 |
| New Write (disk and tape) | |
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$78 |
| New Disk Attach | |
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$7C |
| Open (read of first blocks of a device) | |
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Read/Write Packet
For common command set refer to Appendix A.
DISK. Commands sent to the controller are: Read ($28), and Write ($2A).
For a read or write function, the maximum number of bytes that can be transferred in a single call is 16Mb. If you need more, the command must be broken up into several calls. For controller type 13, the command control field can turn on/off the cache within the drive. If the drive currently has cache in the opposite state as the command control field cache bit, a mode select of page 38 is sent to the controller to turn on/off the cache prior to the read/write command.
TAPE. Commands sent to the controller are: read ($08) and write ($0A).
A tape read or write operation starts at the current position and must be in the correct mode (refer to the appropriate controller manual). To write, the controller must be in general mode or write mode. General mode occurs after
atape positioning command that does not read the tape data
