title: List of SCSI message codes
text: # 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 | |
  