Section 5
SCSI Programming Guidelines
5.11.23.2 VENDOR UNIQUE Mode (001,e)
Not used by ProD rive .
5.11.23.3 PATA Mode (010a1
In this mode, the DATA
OUT
phase contains buffer data. The transfer length (bytes 6-8) specifies the
maximum
~umber
of
bytes that will be transferred during the DATA OUT phase and stored in the buffer.
The initiator should attempt to ensure that the transfer length does not exceed the capacity
of
the buffer.
(The buffer capacity can be determined by the available length field in the READ
BUFFER header.)
If
the
transfer length field specifies a transfer that would exceed the buffer capacity, the
ProDrive will return
CHECK
CONDITION status with a sense key
of
ILLEGAL REQUEST (05H)'
5.11.24
READ BUFFER COMMAND: OPCODE = 3C(hex)
The READ BUFFER command (Table 5-43) is used in conjunction with the WRITE BUFFER command
as a diagnostic function for testing
ProDrive memory and the SCSI bus integrity. This command does
not alter the medium.
TABLE
5-43
READ
BUFFER
Command
Bit 7 6
.,
5
4
3
2
1 o
Byte
0
OPCODE=3CH
1 LOGICAL
UNIT
NUMBER
I
RESERVED
I
MODE
2
BUFFER
ID=O
3-5
RESERVED=O
6-8
(MSB)
ALLOCATION
LENGTH
(lSB)
9
CONTROL
BYTE
BUFFER
ID
(Byte 2) - Must be be set to zero. Any other Buffer ID code will result in a CHECK
CONDITION status with a sense key
of
ILLEGAL REQUEST (05H)'
ALLOCATION
LENGTH
(Bytes 6·8) - Specifies the maximum number
of
bytes the initiator
has allocated for returned information. An allocation length
of
zero indicates that no header
or
data
bytes are to be transferred; any other value indicates the maximum number
of
bytes to
be
transferred.
SCSI Programming Guidelines
5·67
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