Page
120
LTO SCSI Interface Manual
WRITE
The Write command transfers one or more data blocks from the Initiator to the drive.
If the Transfer Length is zero, no data is transferred, and the current position of the
tape is not changed. This condition is not considered an error.
Command Descriptor Block
Byte
Bits
7
6
5
4
3
2
1
0
0
Operation Code (0Ah)
1
Ignored LUN
Reserved
Fixed
2
Transfer Length, MSB
3
Transfer Length
4
Transfer Length, LSB
5
Control
Field Descriptions
Field
Bytes
Bits
Description
Operation
Code
0
The Operation Code for Write is 0Ah.
Ignored
Logical
Unit
1
5-7
The LUN field is residual from the SCSI-1 days and is ignored.
Fixed
1
0
0 = Variable block length. Transfer Length contains the number of
bytes to write.
1 = Fixed block length, as specified by the MODE SELECT Block
Descriptor. Transfer Length contains the number of blocks to
write.
Transfer
Length
2-4
This field specifies the number of bytes (Fixed = 0) or blocks (Fixed
= 1) to be written. A transfer length of 0 is valid and no data is writ-
ten.
Reserved
All reserved bits must be 0.
Control
5
The control field must be 0.
If the Fixed flag is clear, the initiator will transfer a single block of the length indicated
in Transfer Length.
If the Fixed flag is set, the initiator will transfer a sequence of blocks. The Transfer
Length field gives the number of blocks. The current fixed block length gives the
length of the blocks.
At Early Warning, the drive completes the current block transfer and terminates the
command with a Check Condition, EOM bit set, and Sense Key equal to 0. If the
SEW bit (in Mode Select Device Configuration Page) is set, the data in the buffer is
then written to tape.
Subsequent Write commands complete with a Check Condition and the EOM bit set.
If writing the buffer to tape is unsuccessful because of EOT, a Volume Overflow is
reported. The Residual count field in the Request Sense data reports the amount of
data not transferred. Writing can continue in the Early Warning region until EOT is
