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SCSI Commands

5-124 Quantum DLT 4000 Tape Drive

READ BUFFER Command (3Ch) (continued)

Table 5–59 READ BUFFER Header - Field Descriptions

Field Name Description

Available Length This field specifies the total number of data bytes available in the target’s

buffer. This number is not reduced to reflect the allocation length, nor is it

reduced to reflect the actual number bytes written using the WRITE BUFFER

command. Following the READ BUFFER header, the target transfers data from

its data buffer.

5.14.2 Data Mode

In this mode, the DATA IN phase contains only buffer data.

5.14.3 Descriptor Mode

In this mode, a maximum of four bytes of READ BUFFER descriptor information

is returned. The tape drive returns the descriptor information for the buffer

specified by the Buffer ID. In this mode, the drive does not reject the valid Buffer

IDs with a CHECK CONDITION status, but returns all zeros in the READ

BUFFER descriptor.

The Offset Boundary in the following figure is 12 (0Ch), indicating that buffer

offsets should be integral multiples of 4K.

Bit

Byte

7 6 5 4 3 2 1 0

0 Offset Boundaries (0Ch)

1 - 4

(MSB)

Buffer Capacity

(LSB)

Figure 5–61 READ BUFFER Descriptor - Data Format

1 2 ... 219 220 221 222 223 224 225 226 227 228 229 ... 299 300

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