•a reserved field
•the control field
•two or more fields to logically conflicting values If a field has been set to an illegal value:
•CHECK CONDITION status is reported to the host with a sense key of ILLEGAL REQUEST and additional sense of 2400h “invalid field in CDB”.
•The sense key specific bit is set and the sense key specific bytes will be a field pointer.
•The command/data bit is set, indicating that the illegal parameter was in the command.
NOTE: Command descriptor blocks are scanned from left (bit 7) to right (bit 0), and down (from byte 0 to byte n). The field pointer will be set to point to the first bit of the first illegal field encountered using this scanning route. In some cases, where multiple fixed fields are contiguous, the field pointer might be set to point to the first bit of the first fixed field in the group of fixed fields, whereas the actual illegality may lie in a later bit.
Media Access check
This checks if the drive is able to perform media access commands. If the media is inaccessible then CHECK CONDITION status is reported with a sense key of NOT READY. The additional sense will be set to one of the codes associated with the NOT READY key.
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