Date: July 7, 1987 Ref #: __________________________ To: ANSI Committee X3T9.2 From: Dave McIntyre, Michael A. Brown Hewlett Packard Disc Memory Division P. O. Box 39 Boise, ID 83707 Subject: SCSI-2 Group 1, 2, and 5 Command Descriptor Blocks. We are submitting this proposal to replace Table 6-3, Group 1, with the format of the command blocks used throughout the document for defined commands. We are also submitting a proposal to replace Table 6-4, Group 5, with a consistent format. In addition, we would like to propose that a new 10 byte command group, Group 2, be included to provide for the expansion of the 10 byte command set. The LUN field in byte 1 has been replaced with Reserved for the Group 2 and Group 5 CDB's. The Group 5 CDB has been modified to place the Transfer Length on an even byte boundary. This may offer improved access for 16 bit processors. We would like to have these CDB definitions included in the SCSI-2 document at this time to permit the development of chips that recognize and support the new Group 2 and Group 5 formats. Table 6-3: Typical Command Descripter Block for Ten-Byte Group 1 Commands ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code | -----|-----------------------------------------------------------------------| 1 | Logical Unit Number | DPO | FUA | Reserved | RelAdr | -----|-----------------------------------------------------------------------| 2 | (MSB) | -----|--- ---| 3 | | -----|--- Logical Block Address (if required) ---| 4 | | -----|--- ---| 5 | (LSB) | -----|-----------------------------------------------------------------------| 6 | Reserved | -----|-----------------------------------------------------------------------| 7 | (MSB) | -----|--- Transfer Length (if Required) ---| 8 | (LSB) | -----|-----------------------------------------------------------------------| 9 | Control Byte | ============================================================================== Table 6-5: Typical Command Descripter Block for Ten-Byte Group 2 Commands ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code | -----|-----------------------------------------------------------------------| 1 | Reserved | DPO | FUA | Reserved | RelAdr | -----|-----------------------------------------------------------------------| 2 | (MSB) | -----|--- ---| 3 | | -----|--- Logical Block Address (if required) ---| 4 | | -----|--- ---| 5 | (LSB) | -----|-----------------------------------------------------------------------| 6 | Reserved | -----|-----------------------------------------------------------------------| 7 | (MSB) | -----|--- Transfer Length (if Required) ---| 8 | (LSB) | -----|-----------------------------------------------------------------------| 9 | Control Byte | ============================================================================== Table 6-4: Typical Command Descripter Block for Twelve-Byte Group 5 Commands ============================================================================== Bit| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | Byte | | | | | | | | | ============================================================================== 0 | Operation Code | -----|-----------------------------------------------------------------------| 1 | Reserved | DPO | FUA | Reserved | RelAdr | -----|-----------------------------------------------------------------------| 2 | (MSB) | -----|--- ---| 3 | | -----|--- Logical Block Address (if required) ---| 4 | | -----|--- ---| 5 | (LSB) | -----|-----------------------------------------------------------------------| 6 | (MSB) | -----|--- ---| 7 | | -----|--- Transfer Length (if Required) ---| 8 | | -----|--- ---| 9 | (LSB) | -----|-----------------------------------------------------------------------| 10 | Reserved | -----|-----------------------------------------------------------------------| 11 | Control Byte | ==============================================================================