WRITE BUFFER (3Bh)Write Buffer is used with Read Buffer as a diagnostic function for testing the device data buffer, DMAengine, SCSI bus interface hardware, and SCSI bus integrity. Additional modes are provided fordownloading and saving micro code and updating Vendor Unique settings.Bit 7 6 5 4 3 2 1 0Byte0 Operation Code (3Bh)1 LUN Reserved Mode2 Buffer ID3 (MSB)4 Buffer offset5 (LSB)6 (MSB)7 Parameter list length8 (LSB)9 ControlField descriptions:Mode: The Mode field is used to select the mode of operation. The media changer supports the followingvalues within this field.0010b Data0100b Download microcode0101b Download microcode and save1010b Echo bufferIf any non supported value is set, the media changer terminates the command with a CheckCondition status. The sense key will be set to ILLEGAL REQUEST and the sense data to INVALIDFIELD IN CDB.Buffer ID:When the Mode is set to Download micro code or Download micro code and save, the Buffer IDshould be set to zero. When the mode is set to Vendor Unique operation, the Buffer ID indicatesthe requested page to update. If the value of the Buffer ID is not supported by the specified Modethe command is rejected. The target detects and rejects commands that would overrun the buffer.Buffer Offset:The Buffer Offset is required for the Download micro code (and save) modes and optional for theVendor Unique and Data modes. In all other modes the Buffer Offset must be set to zero.Write Data ModeWith this mode, SCSI bus integrity can be tested in conjunction with the READ BUFFER command. Thehost can by means of this mode send up to 256 bytes to the media changer. This data can be retrieved bymeans of the READ BUFFER command. The Buffer Offset specifies the offset within the buffer. Potentialbuffer overruns are detected and will result into a Check Condition the sense key will be set to ILLEGALREQUEST and the additional sense data to INVALID FIELD IN CDB.3-84 TL2000 and TL4000 SCSI Reference
