SCSI target devices provide a number of SCSI diagnostic pages. These can be used by a Send Diagnostic command to tell a target device to run a specialised self-test. The Receive Diagnostic Results command is used where the results from the self-test operation are non-trivial.
Most of the common SCSI devices such as disk-drives support only one or two diagnostic pages. SES devices can support many diagnostic pages.
List of SCSI diagnostic pages
SCSI uses a one byte addressing scheme for diagnostic pages, allowing for a total 256 possible pages. There is a standard map of diagnostic page addresses shown below. Note that any given SCSI device type will only support a subset of these diagnostic pages.
Some diagnostic pages have two different meanings depending on whether they are being used for control purposes (Send Diagnostic command) or to interrogate status (Receive Diagnostic Results command). Those cases are shown as double entries in the table below using this convention: "control definition / status definition".