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Command Specifications
274 C141-C013
(6) Mode = 1, 0, 1, 1 : Echo buffer descriptor
In this mode, a maximum of four bytes of READ BUFFER descriptor information
is returned. The device server shall return the descriptor information for the echo
buffer. The "Buffer Offset" field is reserved in this mode. The allocation length
should be set to four or greater. The device server shall transfer the lesser of the
allocation length or four bytes of READ BUFFER descriptor. The READ
BUFFER descriptor is defined as shown in Table 4.65.
Table 4.65 READ BUFFER command: echo buffer descriptor
Bit
Byte
7 6 5 4 3 2 1 0
0 Reserved EBOS
1 Reserved
2 Reserved Echo Buffer Capacity (MSB)
3 Echo Buffer Capacity (LSB)
The HDD return one in EBOS field, and the HDD verifies that echo buffer data
from each initiator is the same as that previously written by the same initiator.
The "Buffer Capacity" field returns the size of the echo buffer X'0400' in bytes
aligned to a four-byte boundary.