Viper 60s Theory Of Operation And Maintenance Manual page 104

VI/PER SCSI 60, 125 & 150 THEORY OF OPERATION AND MAINTENANCE
5.19 COpy (18h)
The COpy command copies data blocks between a Viper drive and other SCSI Sequential or
Direct Access devices. Viper drives manage data transfers by assuming the role of Initiator to
establish a logical connection with another device. Viper drives do not support third party
copying or managing transfers between two remote devices. The drive manages transfers
only between itself and another device.
5.19.1 Command Descriptor Block
6
o
o
o
o o
Parameter List Length - MSB
Parameter List Length
4
Parameter List Length - LSB
5
5.19.2 Command Descriptor Block Field Description
The Parameter List Length field , Bytes 2 to
41
contains the total number of bytes in the trailing
parameter list , including the 4-byte Header plus all 12-byte Segment Descriptors.
The Parameter List Length must be divisible by the 12-byte Segment Descriptor plus 4-byte
header. Examples of valid quantities are: 0
1 41
16
1
28
1
40. If the Parameter List Length does not
meet the above criteria ,
it is terminated with Check Condition and Illegal REQUEST SENSE
Key.
5.19.3 COPY Command Description
The COpy command can include up to 256 Segment Descriptors, each identifying a different
device or, for Direct Access devices, starting block address. The Viper drive processes one
Segment Descriptor at a time. The Viper drive tape is not rewound between processing of
each Segment Descriptor.
A copy to or from a Direct Access (D/ A) device can be disk, image, or individual file. Each
Segment Descriptor only transfers contiguous files from the D/ A device. File transfers that
are not contiguous blocks on the D / A device can be accomplished by using multiple Segment
Descriptors to a maximum of 256.
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