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Command Specifications
3 -
110
C141-E167
The "Addressing boundary" field in the buffer descriptor indicates the addressing boundary in the
data buffer which can be specified in the WRITE BUFFER Command and the READ BUFFER
Command as a "Power" when expressed as a "Power of 2." The IDDs report X'02' (=2
2
), indicating
that it is possible to specify the address in 4-byte units. Also, the "Buffer capacity" field indicates
the byte length of the size of the data buffer which can be operated by the WRITE BUFFER and
READ BUFFER commands.
Note: Exercise caution regarding the following points when using this command.
If the WRITE BUFFER command or READ BUFFER command is used under a multi-initiator
or multitask environment, it is necessary to be careful of the contents of the data buffer being
changed by another initiator or a command that issues another task during the interval between
completion of WRITE BUFFER command execution and execution of the READ BUFFER
command.
(5) Mode = 1, 0, 1, 0 : Echo buffer
In this mode the IDD transfers data to the INIT from the echo buffer. The echo buffer shall transfer
the same data as when the WRITE BUFFER command with the mode field set to echo buffer was
issued. The BUFFER ID and BUFFER OFFSET fields are ignored in this mode.
(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 Figure 3.27.
Bit
Byte
76543210
0 Reserved EBOS
1 Reserved
2 Reserved Echo Butffer Capacity (MSB)
3 Echo Buffer Capacity (LSB)
Figure 3.27 READ BUFFER command: Echo buffer descriptor
The IDD return one in EBOS field, and the IDD 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'01FC' in bytes aligned to a four-byte
boundary.