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CUSTOM SCSI PACKETS
Introduction
The SCSI firmware requests "canned" functions from SCSI disk controllers and
from SCSI tape controllers. Some of these functions are disk read and write,
disk format, tape read and write, and tape positioning operations. The
"canned" functions are only provided for the supported SCSI devices that are
listed in the Equipment Supported section in Chapter 1.
If you want to perform a function that is not "canned", or you want to
communicate with SCSI devices that are not supported by the SCSI firmware,
you do not have to rewrite the SCSI firmware. Any SCSI operation may be
performed through the use of the custom SCSI packet.
A custom SCSI packet may be used for a variety of needs. Following are some
typical needs:
1. You need to perform a command on a supported SCSI disk controller that
is not "canned" in the SCSI firmware. (For example, an offline COPY
command is not supported directly by the SCSI firmware. You may
perform this COPY command through the custom SCSI packet.)
2. You wish to interface the MVME147 module to a SCSI optical disk
controller.
3. You wish to request linked commands from a disk controller.
There are three classes of custom SCSI packets, described in the following
sections. They are:
Initiator role custom packet
TARGET enable custom packet
TARGET sequence custom packet
Initiator Role Custom Packet
The initiator role custom packet is shown in the following table.
Even Byte \
Odd Byte \