Viper 60s Theory Of Operation And Maintenance Manual page 108

VI/PER SCSI 60, 125 & 150 THEORY OF OPERA TlON AND MAINTENANCE
5.19.7 SEQ to D/A Segment Descriptor
The Segment Descriptor for COpy Function Code 01h initiates a WRITE command from the
SEQ device (Viper drive) to the
0/
A device.
The Viper drive must be the source device in a SEQ to
0/
A copy. Byte 0, bits 0 to 2 (Source
LUN) have value 0, referencing the controllers single drive. Bytes 2 to 3 (SEQ Device Block
Length) have value 512 (200 Hext according to the Viper drive recording format.
In the case where the
0/
A device block size is 256, the 24-bit count in
0/
A Device Number of
Blocks must be an even number.
A block count of zero is permitted and causes a WRITE type command to be issued to the
0/
A device with a Transfer Length of zero. This is not considered an error.
This type of WRITE command is a function of the value in
0/
A Device Logical Block Address.
If the value of the Logical Block Address is equal to or greater than 221, a WRITE Extended
(2Ah) is used. When the READ Extended is required, the ReI Adr Bit, Byte I, Bit I, is not used.
5.19.7.1 SEQ to D/A
1::'.
'j
Jtor Block
I
I
I
I
BITS
7
I
6 5 4
3
2 1 0
BYTES
• 0
•
Source SCSIID Po 0 Source LUN
1 Destination SCSIID 0 Des!. LUN
2 0 0 0 0 0 0
1
0
3 0 0 0 0 0 0 0 0
4
D/A Device Number of Blocks - MSB
5 D/A Device Number of Blocks
6 D/A Device Number of Blocks
7
D/A Device Number of Blocks - LSB
8
D/A Device Logical Block Address - MSB
9
D/A Device Logical Block Address
10 D/A Device Logical Block Address
11 D/A Device Logical Block Address - LSB
mmmJ
mm.
5-50