SCSI Inquiry Command
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The SCSI Inquiry command is used to obtain basic information from a target device. The CDB structure is:
| bit→ ↓byte |
7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|---|---|---|---|---|---|---|---|---|
| 0 | Operation code = 12h | |||||||
| 1 | LUN | Reserved | EVPD | |||||
| 2 | Page code | |||||||
| 3 | Reserved | |||||||
| 4 | Allocation length | |||||||
| 5 | Control | |||||||
If the EVPD parameter bit is zero and the Page Code parameter byte is zero then the target will return the standard inquiry data which is structured like this:
| bit→ ↓byte |
7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|---|---|---|---|---|---|---|---|---|
| 0 | Peripheral qualifier | Peripheral device type | ||||||
| 1 | RMB | Device-type modifier | ||||||
| 2 | ISO version | ECMA version | ANSI-approved version | |||||
| 3 | AEC | TrmIOP | Reserved | Response data format | ||||
| 4 | Additional length (n-4) | |||||||
| 5 | Reserved | |||||||
| 6 | Reserved | |||||||
| 7 | RelAdr | WBus32 | WBus16 | Sync | Linked | Reserved | CmdQue | SftRe |
| 8–15 | Vendor identification (ASCII) | |||||||
| 16–31 | Product identification (ASCII) | |||||||
| 32–35 | Product revision level | |||||||
| 36–55 | Vendor-specific | |||||||
| 56–95 | Reserved | |||||||
| 96 | Vendor-specific parameters (variable number of bytes) | |||||||
The special fields in the standard inquiry data have the following meaning:
- Peripheral Device Type - see separate article on SCSI Peripheral Device Types
- RMB - removable medium
- AENC - 1 = supports Asynchronous Event Notifications - (processor devices only)
- TrmIOP - 1 = supports Terminate I/O Process messages
- Response data format - 000=SCSI compliant, other values = legacy devices
- RelAdr - 1= this LUN supports Relative Addressing Mode (linked commands only)
- WBus32+WBus16 - support for wide data buses:
- 00 - 8-bit only
- 01 - 8 or 16-bit
- 11 - 8, 16 or 32 bit
- Sync - 1 = supports synchronous transfers
- Linked - 1 = this LUN supports linked commands
- CmdQue - 1 = supports Tagged Command Queuing
- SftRe - 1 = performs soft resets
If the EVPD parameter bit is one then the target will return Vital Product Data (VPD). This can be from one of a number of different pages, depending on the value of the Page Code parameter:
- 00h - Supported vital product data
- 01h-7Fh - ASCII information
- 80h - Unit serial number
- 81h - Implemented operating definitions
- 82h - ASCII implemented operating definition
- 83h-BFh - Reserved
- C0h-FFh - Vendor-specific
