Write Buffer - 3Bh

The library will receive a requested buffer of data and write it to the appropriate internal storage.

This command can be used primarily for enhanced domain validation (using the echo buffer mode). The initiator can either transfer the data with a single WRITE BUFFER command, or it can also transfer it in blocks utilizing offsets into the buffer.

The WRITE BUFFER CDB format is shown in the following table.

Table 1: WRITE BUFFER CDB format

Bit

Byte

7

6

5

4

3

2

1

0

0

Op Code (3Bh)

1

Logical Unit Number

Rsvd

Mode

2

Buffer ID

3

:

5

Buffer Offset

6

:

8

Parameter List Length

9

Control
Field Description
Mode

The supported modes are:

  • 2h – Data
  • Ah – Echo Buffer

In Data Mode, an amount of data specified by the Parameter List Length is targeted for the buffer defined by the Buffer ID field, starting at the specified Buffer Offset. Buffer IDs are assigned beginning with zero, and are assigned contiguously. Buffer ID code assignments for the WRITE BUFFER command are the same as for the READ BUFFER command.

In Echo Buffer Mode, the amount of data specified by the Parameter List Length is transferred from the initiator to the echo buffer. The Buffer ID and Buffer Offset fields are ignored in this mode.

Note: The Echo Buffer is supported only if the library control path is provided by a tape drive.
Buffer ID

This field specifies which buffer the request is for. The IDs are the same for both the READ BUFFER and WRITE BUFFER commands. The IDs supported by the library, along with their primary use, are listed in Table 2.
Buffer Offset

This field indicates the starting location (byte offset) within the specified buffer to write data. The initiator should conform to the offset boundary requirements returned in the READ BUFFER descriptor described in “Read Buffer Response.”
Parameter List Length

If applicable, this field should be set to indicate the amount of data being written.