List of SCSI message codes
# List of SCSI message codes

This is a list of SCSI message codes.

A SCSI message code is a computer term which defines how SCSI devices send interface management information. The message code comprises one or more bytes.

## List of message formats

The first byte of the message determines the format:

| Value | Message format |
| - | - |
| 00h | One-byte message (COMMAND COMPLETE) |
| 01h | Extended messages |
| 02h-1Fh | One-byte messages |
| 20h-2Fh | Two-byte messages |
| 30h-7Fh | Reserved |
| 80h-FFh | One-byte message (IDENTIFY) |

## List of message codes

| Value | Message name | Format |
| - | - | - |
| 00h | COMMAND COMPLETE | |
| 01h | EXTENDED MESSAGE | 01nnyy... - nn is the length, yy is the extended message code |
| 02h | SAVE DATA POINTER | |
| 03h | RESTORE POINTERS | |
| 04h | DISCONNECT | |
| 05h | INITIATOR DETECTED ERROR | |
| 06h | ABORT | |
| 07h | MESSAGE REJECT | |
| 08h | NO OPERATION | |
| 09h | MESSAGE PARITY ERROR | |
| 0Ah | LINKED COMMAND COMPLETE | |
| 0Bh | LINKED COMMAND COMPLETE (WITH FLAG) | |
| 0Ch | BUS DEVICE RESET | |
| 0Dh | ABORT TAG | |
| 0Eh | CLEAR QUEUE | |
| 0Fh | INITIATE RECOVERY | |
| 10h | RELEASE RECOVERY | |
| 11h | TERMINATE I/O PROCESS | |
| 12h-1Fh | Reserved | |
| 20h | SIMPLE QUEUE TAG | 20nn - where nn is the queue tag |
| 21h | HEAD OF QUEUE TAG | 21nn - where nn is the queue tag |
| 22h | ORDERED QUEUE TAG | 22nn - where nn is the queue tag |
| 23h | IGNORE WIDE RESIDUE | 230i - where i is the number of bytes to ignore (can be 1, 2 or 3) |
| 24h-2Fh | Reserved for two-byte messages | |
| 30h-7Fh | Reserved | |
| 80h-FFh | IDENTIFY | |

## List of extended message codes

| Value | Length | Message name | Format |
| - | - | - | - |
| 00h | 05h | MODIFY DATA POINTER | 010500aaaa - where aaaa is added to the current data pointer |
| 01h | 03h | SYNCHRONOUS DATA TRANSFER REQUEST | 010301pprr - where pp is the period and rr is the REQ/ACK offset |
| 02h | nn | Reserved - was formerly used for the EXTENDED IDENTIFY message in SCSI-1 | 01nn02... |
| 03h | 02h | WIDE DATA TRANSFER REQUEST | 010203ee - where ee is the transfer width exponent |
| 04h-7Fh | | Reserved | |
| 80h-FFh | | Vendor-specific | |
