Quantum DLT 4700, Руководство по эксплуатации продукта

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DLT4000 SCSI Interface
8-10 DLT4000/DLT4500/DLT4700 Cartridge Tape Subsystem
When received from an initiator, the tape drive may respond in one of two ways.
First, it may take the message as a request by the initiator to disconnect and comply by
entering message in phase and sending the DISCONNECT message back to the
initiator (possibly preceded by the SAVE DATA POINTERS message). In this case, it
will delay a minimum of 200
µ
s before arbitrating for the bus again. Alternately, it
may enter the message in phase and return MESSAGE REJECT.
EXTENDED MESSAGE (01h)
This is sent as the first byte of a multiple-byte message (> 2 bytes) by either initiator or
target. EXTENDED MESSAGE has the following format:
Byte 0 Extended Message Identifier – 01h
Byte 1 Extended Message Length
Byte 2 Extended Message Code
Byte 3 Extended Message Additional Parameters
Figure 8-1 Extended Message Format
The Extended Message Length specifies the length of the Extended Message plus the
number of additional parameter bytes that are to follow. The length does not include
bytes 0 and 1. A value of zero for the Extended Message Length indicates 256 bytes to
follow.
Possible Extended Message codes are:
00h - MODIFY DATA POINTER (not supported)
01h - SYNCHRONOUS DATA TRANSFER REQUEST (See page 8-13)
02h - Reserved
03h - WIDE DATA TRANSFER REQUEST (not supported)
04h-7Fh - Reserved
80-FFh - Vendor Unique (See page 8-21)
If the tape drive receives an extended message which it does not support, it switches to
message in phase and returns MESSAGE REJECT after all the bytes of the message
have been transferred.