Parameter List check
For LOG SELECT, MODE SELECT and some diagnostic commands, the associated data sent to the drive is in the form of parameter lists. These are described under the command names in the next chapter. Checks are performed to test the following:
•Fixed and reserved fields have not been modified. Fixed fields are indicated by a number in round brackets following the field name.
•A field has been set to an invalid value.
•The syntax of the page of parameters has been
If a field has been set to an illegal value, CHECK CONDITION is reported to the host with a sense key of ILLEGAL REQUEST and additional sense of 2600h (invalid field in parameter list).
The drive scans the data in the Command Description Block from “left” (bit 7) to “right”, and “down” (from byte 0 to byte n). It sets the field pointers to the first bit of the first bad field encountered. If the bad field is contained in a contiguous group of fixed fields, the pointers indicate the first bit of the first field in the group, even though the error may be in a later field in the group.
NOTE: With MODE SELECT, the drive checks the integrity of the whole parameter list before acting on any parameters, so all the mode parameters need to be correct before any of them are implemented.
Reservation check
This checks to see if the drive has been reserved for use by a host, and if it has, whether the host is the same host that sent the command being executed.
If the drive has been reserved for some other host then RESERVATION CONFLICT status is reported.
See the RESERVE UNIT (page 164) and RELEASE UNIT (page 135) commands.
Unit Attention check
This checks if a UNIT ATTENTION condition exists for the host which sent the command. If it does, the drive reports CHECK CONDITION status with a sense key of UNIT ATTENTION. The remaining sense data will be set according to the unit attention condition which exists. See Unit Attention Sense in the description of the REQUEST SENSE command on page 155.
34