Tandberg Data
Verify
29-2
Tandberg SLR Product Line SCSI Functional Specifications
29.2. Command Descriptor Block
BYTE
BIT 7
6
5
4
3
2
1
0
00
Operation Code
13h
01
Logical Unit Number (LUN)
RESERVED
IMM
CMP
FIX
02
Verification Length
03
04
05
Control Byte
Table 29-1: VERIFY Command Descriptor Block
IMM
The immediate (IMM) bit is ignored by the Drive.
When byte-by-byte data compare is performed (CMP bit is
set to one), the Drive sends status immediately after
data transfer. Since the Drive compares data at the
SCSI-bus side of the data buffer, the VERIFY command is
terminated when status is sent.
When only CRC/ECC check is performed (CMP bit set to
zero) the VERIFY command does not return with status
until all the requested data has been verified.
CMP
A Byte Compare (CMP) bit of zero indicates that the
verification will be simply a CRC/ECC verification. No
data will be transferred between the Initiator and the
Drive. The VERIFY command will then be functionally
equivalent to a SPACE block forward command (without the
FAST option).
A CMP bit of one indicates that a byte-by-byte compare
of the data on tape and the data transferred from the
Initiator will be performed by the Drive. Data will be
transferred from the Initiator to the Drive as in a
WRITE command.
FIX
A Fixed (FIX) bit of zero indicates that a single block
will be verified with the Verification Length specifying
the expected length of the block in number of bytes to
be verified.
A FIX bit of one indicates that the Verification Length
specifies the number of blocks to be verified beginning
with the next logical block. Note that a FIX bit of one
is not allowed when the Drive is in Variable Block mode
(see the Block Size field in the Block Descriptor List
of the MODE SELECT command for further details).
Verification Length
This field specifies the number of bytes or blocks
requested for verification. Any value in the range
0..16777215 is legal. Note, however, that the maximum
block size that can be written is 262144 bytes.
