IBM DDRS-39130 Hard Drive Specifications - Page 138

Read Data Mode 010b, Descriptor Mode 011b

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76 BYTE 0 BYTE 1 (MSB) BYTE 2 BYTE 3 BIT 5432 RSVD = 0 Buffer Capacity 10 (LSB) Figure 98. READ BUFFER Header The buffer capacity specifies the total number of data bytes that are available in the file's data buffer. This number is not reduced to reflect the allocation length nor is it reduced to reflect the actual number of bytes written using the WRITE BUFFER command. Following the READ B U F F E R header, the file will transfer data from its data buffer. 7.18.2 Read Data (Mode 010b) In this mode, the DATA IN phase contains buffer data. Buffer ID field must be set to zero, indicating the data transfer buffer. If another value is specified, the command is terminated with CHECK CONDITION status. File shall set sense key to ILLEGAL REQUEST and additional sense code to ILLEGAL FIELD IN CDB. Buffer Offset specifies the offset of the memory space specified by the Buffer ID. The initiator should conform to the offset boundary requirements returned in the READ B U F F E R descriptor. If the value exceeds the buffer specified, the command is terminated with CHECK CONDITION status. File shall set sense key to ILLEGAL REQUEST and additional sense code to ILLEGAL FIELD IN CDB. Allocation Length The file terminates the DATA IN phase when allocation length bytes of data have been transferred or when the header and all available data have been transferred to the initiator, whichever is less. 7.18.3 Descriptor (Mode 011b) In this mode, a maximum of four bytes of R E A D B U F F E R descriptor information are returned. The file returns the descriptor information for the buffer specified by the Buffer ID. Buffer ID field should normally be set to zero indicating the file data transfer buffer. If any other value is specified the file returns all zeros in the R EAD B U F F E R descriptor. Buffer Offset field is reserved. Allocation Length must be set to four or greater. The file transfers the lesser of the allocation length or four bytes of READ B U F F E R descriptor. The READ B U F F E R descriptor is defined in Figure 99 on page 129. 128 OEM Spec. of DDRS-3xxxx

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BIT
7
6
5
4
3
2
1
0
BYTE 0
RSVD = 0
BYTE 1 (MSB)
Buffer Capacity
BYTE 2
BYTE 3
(LSB)
Figure 98. READ BUFFER Header
The buffer capacity specifies the total number of data bytes that are available in the file's data buffer. This
number is not reduced to reflect the allocation length nor is it reduced to reflect the actual number of bytes
written using the WRITE BUFFER command.
Following the READ BUFFER header, the file will transfer data from its data buffer.
7.18.2
Read Data (Mode 010b)
In this mode, the DATA IN phase contains buffer data.
Buffer ID
field must be set to zero, indicating the data transfer buffer.
If another value is specified, the
command
is terminated
with
CHECK
CONDITION
status.
File
shall
set
sense
key
to
ILLEGAL
REQUEST and additional sense code to ILLEGAL FIELD IN CDB.
Buffer Offset
specifies the offset of the memory space specified by the Buffer ID.
The initiator should
conform to the offset boundary requirements returned in the READ BUFFER descriptor.
If the value
exceeds the buffer specified, the command is terminated with CHECK CONDITION status.
File shall set
sense key to ILLEGAL REQUEST and additional sense code to ILLEGAL FIELD IN CDB.
Allocation Length
The file terminates the DATA IN phase when allocation length bytes of data have been
transferred or when the header and all available data have been transferred to the initiator, whichever is less.
7.18.3
Descriptor (Mode 011b)
In this mode, a maximum of four bytes of READ BUFFER descriptor information are returned.
The file
returns the descriptor information for the buffer specified by the Buffer ID.
Buffer ID
field should normally be set to zero indicating the file data transfer buffer. If any other value is
specified the file returns all zeros in the READ BUFFER descriptor.
Buffer Offset
field is reserved.
Allocation Length
must be set to four or greater.
The file transfers the lesser of the allocation length or four
bytes
of
READ
BUFFER
descriptor.
The
READ
BUFFER
descriptor
is
defined
in
Figure 99
on
page 129.
128
OEM Spec. of DDRS-3xxxx