HP Surestore 28/48-Slot with DLT7000 Digital Linear Tape SCSI-2 Drive and SCSI - Page 36

SCSI Command Overview Library Control Commands Message Reject 07, The initiator or target sends this message to indicate that one or more bytes in the last message received was inappropriate or has not been implemented. To indicate that it intends to send this message, the initiator asserts the ATN signal before it releases ACK for the REQ/ACK handshake of the message to be rejected. MESSAGE REJECT indicates messages that the drive considers illegal or unsupported. The tape device will send this message to the initiator before requesting additional message bytes. No Operation 08H, If a target requests a message, the initiator sends NO-OP if it does not have another valid message to send. The message is accepted when the drive is acting as a target, and may be sent when it is an initiator. If the target receives this message during a selection, the drive proceeds to the COMMAND phase (provided ATN does not continue being asserted). The NO-OP message is ignored by the tape drive. Message Parity Error 09H, The initiator sends this message to the target to indicate that one or more bytes in the last message had a parity error. To indicate that it intends to send the message, the following occurs: • The initiator sets the ATN signal before it releases ACK for the REQ/ACK handshake of the message with the parity error. This provides an interlock so that the target can determine which message has the parity error. If the target receives this message under other conditions, it proceeds to the BUS FREE state by releasing the BSY signal, signifying a catastrophic error. • The target will respond by switching to the Message In phase and resending all the message bytes that generated the original MESSAGE PARITY ERROR message. 1- 12 Chapter 1