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Quantum DLT 7000 Tape System 5-135
READ BUFFER Command (3Ch) (continued)
5.14.1 Combined Header and Data Mode
In this mode, the tape drive returns a 4-byte header followed by data bytes. The
drive terminates the DATA IN phase when the Allocation Length bytes of
header and data have been transferred or when all available data has been
transferred to the initiator, whichever is less. The 4-byte READ BUFFER header
is followed by data bytes from the target data buffer. The figure below illustrates
the format of the header.
Bit
Byte
7 6 5 4 3 2 1 0
0 Reserved
1 - 3
(MSB)
Available Length
(LSB)
Figure 5–65 READ BUFFER Header - Data Format
Table 5–64 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.