Dell PowerVault ML6000 Dell PowerVault ML6000 SCSI Reference Guide - Page 66

Read Buffer Response, Buffer ID, Buffer Offset, Allocation Length, Offset Boundary, Table 53

Get Dell PowerVault ML6000 PDF manuals and user guides View all Dell PowerVault ML6000 manuals
Add to My Manuals
Save this manual to your list of manuals

Page 66 highlights

In Echo Buffer Mode, data is transferred to the initiator from the echo buffer. The echo buffer will transfer the same data that was received from the last WRITE BUFFER command sent with Echo Buffer Mode. If the allocation length is insufficient to accommodate the number of bytes of data as received in the prior echo buffer mode WRITE BUFFER command, the returned data will be truncated. This is not considered an error. If a prior echo buffer mode WRITE BUFFER command was not successfully completed the echo buffer mode READ BUFFER will return a Check Condition, with a Sense Key of Illegal Request and additional sense code of Command Sequence Error. The data may be read from the echo buffer multiple times. In Echo Buffer Descriptor Mode, a maximum of four bytes of READ BUFFER descriptor information is returned for the echo buffer. The Buffer Offset field is reserved in this mode. The allocation length should be set to at least four for this mode. See Table 53 for a definition of the READ BUFFER descriptor. Buffer ID - This field specifies which buffer the request is for. The IDs are the same for both the READ BUFFER and WRITE BUFFER commands. The IDs supported by the library, along with their primary use (data or download modes), are listed in the following table. Table 53 Supported Buffer IDs Buffer ID Description Read/Write 0 Library Firmware Write Additional Buffer IDs beyond those listed are reserved. Descriptor Mode can be used to determine the size or capacity of a given buffer. Buffer Offset - This field contains the byte offset within the specified buffer from which data shall be transferred. The initiator should conform to the offset boundary requirements returned in the READ BUFFER descriptor described in "Read Buffer Response." Allocation Length - In Data Mode, this field should be set to accommodate the amount of data being requested for return. In Descriptor Mode, this field should be set to at least four. Read Buffer Response In Data Mode, the requested buffer of data is returned per the buffer offset and allocation length. In Descriptor Mode, a buffer descriptor is returned as shown in the following table. Table 54 Read Buffer Response Byte Bit 7 6 5 4 3 2 1 0 0 Offset Boundary 1 Buffer Capacity 3 Offset Boundary - This field returns the boundary alignment (byte boundary) within the selected buffer for subsequent READ BUFFER commands. The value contained in this field is interpreted as a power of two. 56 SCSI Commands

  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 14
  • 15
  • 16
  • 17
  • 18
  • 19
  • 20
  • 21
  • 22
  • 23
  • 24
  • 25
  • 26
  • 27
  • 28
  • 29
  • 30
  • 31
  • 32
  • 33
  • 34
  • 35
  • 36
  • 37
  • 38
  • 39
  • 40
  • 41
  • 42
  • 43
  • 44
  • 45
  • 46
  • 47
  • 48
  • 49
  • 50
  • 51
  • 52
  • 53
  • 54
  • 55
  • 56
  • 57
  • 58
  • 59
  • 60
  • 61
  • 62
  • 63
  • 64
  • 65
  • 66
  • 67
  • 68
  • 69
  • 70
  • 71
  • 72
  • 73
  • 74
  • 75
  • 76
  • 77
  • 78
  • 79
  • 80
  • 81
  • 82
  • 83
  • 84
  • 85
  • 86
  • 87
  • 88
  • 89
  • 90
56
SCSI Commands
In
Echo Buffer Mode
, data is transferred to the initiator from the echo buffer. The echo buffer will transfer
the same data that was received from the last WRITE BUFFER command sent with Echo Buffer Mode. If
the allocation length is insufficient to accommodate the number of bytes of data as received in the prior echo
buffer mode WRITE BUFFER command, the returned data will be truncated. This is not considered an error.
If a prior echo buffer mode WRITE BUFFER command was not successfully completed the echo buffer
mode READ BUFFER will return a Check Condition, with a Sense Key of Illegal Request and additional
sense code of Command Sequence Error. The data may be read from the echo buffer multiple times.
In
Echo Buffer Descriptor Mode
, a maximum of four bytes of READ BUFFER descriptor information is
returned for the echo buffer. The Buffer Offset field is reserved in this mode. The allocation length should
be set to at least four for this mode. See
Table 53
for a definition of the READ BUFFER descriptor.
Buffer ID
– This field specifies which buffer the request is for. The IDs are the same for both the READ
BUFFER and WRITE BUFFER commands. The IDs supported by the library, along with their primary use
(data or download modes), are listed in the following table.
Additional Buffer IDs beyond those listed are reserved. Descriptor Mode can be used to determine the size
or capacity of a given buffer.
Buffer Offset
– This field contains the byte offset within the specified buffer from which data shall be
transferred. The initiator should conform to the offset boundary requirements returned in the READ
BUFFER descriptor described in “Read Buffer Response.”
Allocation Length
– In Data Mode, this field should be set to accommodate the amount of data being
requested for return. In Descriptor Mode, this field should be set to at least four.
Read Buffer Response
In Data Mode, the requested buffer of data is returned per the buffer offset and allocation length.
In Descriptor Mode, a buffer descriptor is returned as shown in the following table.
Offset Boundary
– This field returns the boundary alignment (byte boundary) within the selected buffer for
subsequent READ BUFFER commands. The value contained in this field is interpreted as a power of two.
Table 53
Supported Buffer IDs
Buffer ID
Description
Read/Write
0
Library Firmware
Write
Table 54
Read Buffer Response
Bit
Byte
7
6
5
4
3
2
1
0
0
Offset Boundary
1
Buffer Capacity
3