TAPE UNIT SCSI COMMANDS

M2488 PRODUCT GUIDE

4-3.31 WRITE command 0Ah

The WRITE command transfers one or more blocks from the initiator to the current position on the logical unit.

4-3.31.1 WRITE CDB Description

WRITE is a six-byte command. The bytes are as shown below and described in Table 4-128. Common fields are described in paragraph 4-3.1 on page 4-4.

 

 

 

 

 

 

 

 

 

 

 

BITS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BYTES

7

 

 

6

 

5

 

4

 

3

 

2

1

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

0

 

 

0

 

0

 

0

 

1

 

0

1

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LUN

 

 

 

 

 

 

 

Reserved

 

 

 

 

Fixed

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

MSB

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Transfer Length

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LSB

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reserved

 

 

 

 

 

Flag

 

 

Link

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Note: Changeable fields in the CDB are shaded.

Table 4-128. WRITE Field Description

BYTE

BIT

VALUE

DESCRIPTION

 

 

 

 

0

0-7

0Ah

Operation code.

 

 

 

 

1

0

 

The Fixed bit specifies both the meaning of the transfer length field and

 

 

 

whether fixed-length or variable-length blocks are to be transferred.

 

 

 

If the Fixed bit is zero, a single block is transferred with the bytes trans-

 

 

 

ferred being the lesser of the actual block length or the requested transfer

 

 

 

length.

 

 

 

If the Fixed bit is one, the transfer length specifies the number of blocks to

 

 

 

be transferred to the initiator.

 

 

 

 

2-4

 

 

The Transfer Length indicates the number of bytes or blocks to transfer.

 

 

 

The block length used is the current block length specified in the mode

 

 

 

parameters block descriptor (refer to the Mode Select Block Descriptor in

 

 

 

Table 4-47 on page 4- 53.)

 

 

 

When the transfer length is zero, no data is transferred and the current

 

 

 

position on the logical unit is not changed. This condition is not considered

 

 

 

an error.

 

 

 

 

4-3.31.2 WRITE CHECK CONDITION Status

This control unit implements both fixed-block and variable-block modes. Reference the Read Block Limits and Mode Select (mode parameters block descriptor) commands for more informa- tion about fixed and variable block modes. If the Fixed bit is one and the current mode is variable (as set by MODE SELECT command or default power on condition) the command is rejected with

4-140

CG00000-011503 REV. A

April 1997

Page 222
Image 222
Fujitsu M2488 manual Write command 0Ah, Write CDB Description, Write Field Description, Write Check Condition Status