Viper 60s Theory Of Operation And Maintenance Manual page 106

VI/PER SCSI 60, 125 & 150 THEORY OF OPERATION AND MAINTENANCE
5.19.5 Parameter List Header Block Field Descriptions
COpy
o
3-7
DESCRIPTION
This field is ignored since Viper drives do not
queue commands. The COpy command must
complete before a subsequent command is
accepted.
In this field the Parameter List Header specifies
the format Function of the subsequent Segment
Descriptors. Viper drives use a Code subset of
the COpy command functions defined in ANSI
X3 .131 , restricted by the Viper requirement that
the drive be considered a sequential device when
participating in a COpy command.
The following shows Copy functions supported in terms of standard copy function Codes.
COpy FUNCTION
i
D/A
to SEQ
SEQ to
D/A
SEQ to SEQ
D/A
=
Direct Access Device
SEQ
=
Sequential Device
RESTRICTION
Source device cannot be a Viper drive.
Destination cannot be a Viper drive.
Device cannot copy to itself.
In the following Segment Descriptors, designation of SCSI ID for a Viper drive must match the
SCSI ID configured on the Viper drives Configuration Jumper Block.
5.19.6 D/A to SEQ Segment Descriptor
The Segment Descriptor for COpy Function Code OOh initiates a READ from the D / A device
and a WRITE to the SEQ device (Viper drive). The Viper drive must be the destination device
in a D/ A to SEQ copy, Destination LUN, Byte 1, Bits 0-2, has a value of 0, referencing the
controllers single drive.
When the D/ A device block size is 256, the 24-bit count in D/ A Device Number of Blocks
must be an even number, indicating a whole number of 512 byte transfers. A block count of
zero is permitted and causes a READ to be issued to the D / A device with a Transfer Length of
zero. This is not considered an error.
This type of READ is a function of the value in D / A Device Logical Block Address. If the value
of the Logical Block Address is equal to or greater than 221, a READ Extended (28h) is used.
When the READ Extended is required, the ReI Adr Bit, Byte 1, Bit 1, is not used.
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