Technical data

B.5 SCSI Message System
The SCSI message system allows communication between an initiator and a target for the
purpose of interface management.
A message may be one, two or multiple bytes in length. One or more messages may be sent
during a single Message phase, but a message may not be split over Message phases. The
initiator is required to end the Message Out phase (by negating AN) when it sends certain
messages.
B.5.1 Messages — Format and Codes
One-byte, two-byte, and extended message formats are defined. The first byte of the message
determines the format as follows:
Table B–5: Messages — Format and Codes
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 for future standardization
80h-FFh One-byte message (IDENTIFY)
B–6 Small Computer System Interface (SCSI)