<!--
{
  "availability" : [
    "DriverKit: 22.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "SCSIPeripheralsDriverKit",
  "identifier" : "/documentation/SCSIPeripheralsDriverKit/SCSIDeviceOutParameters/fCommandDescriptorBlock",
  "metadataVersion" : "0.1.0",
  "role" : "Instance Property",
  "symbol" : {
    "kind" : "Instance Property",
    "modules" : [
      "SCSIPeripheralsDriverKit"
    ],
    "preciseIdentifier" : "c:@S@SCSIDeviceOutParameters@FI@fCommandDescriptorBlock"
  },
  "title" : "fCommandDescriptorBlock"
}
-->

# fCommandDescriptorBlock

A 16-byte opcode to fill out the Command Descriptor Block (CDB).

```
SCSICommandDescriptorBlock fCommandDescriptorBlock;
```

## Discussion

Populate this member of the parameters structure with the functions listed in the following sections:

- Creating common SCSI commands
- Creating Self-Monitoring, Analysis and Reporting Technology (SMART) Commands
- Creating arbitrary SCSI commands

---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)