Technical information

HGST Ultrastar C15K600 Hard Disk Drive Specification
166
18.10.4
Mode Page 02 (Disconnect/Reconnect Parameters)
Table 137 Mode Page 02 (Disconnect/Reconnect Parameters)
Byte
Bit
Default
7
6
5
4
3
2
1
0
0
PS 0 Page Code = 02h
82h
1
Page Length = 0Eh
0Eh
2
Read Buffer Full Ratio
00h
3
Write Buffer Empty Ratio
00h
4-5
(MSB)
Bus Inactivity Time Limit
(LSB)
00h
6-7
Disconnect Time Limit = 0
00h
8-9
(MSB)
Maximum Connect Time Limit
(LSB)
00h
10-11
(MSB)
Maximum Burst Size
(LSB)
00h
12-13
Reserved = 0
00h
14-15
First Burst Size = 0
00h
The disconnect/reconnect page provides the Initiator with the means to tune the performance of the SAS Link.
The drive uses the disconnect/reconnect parameters to control when it attempts to regain control of the link during
READ (operation code 08h and 28h) and WRITE (0Ah, 2Ah and 2E).
- Read Buffer Full Ratio is the numerator of a fraction whose denominator is 256. The fraction indicates how full
the drive data buffer should be before attempting to re-arbitrate for the link. If the ratio is set to 0h, the target will
calculate and use an optimal ratio based on the negotiated transfer rate.
- Bus Inactivity Time Limit specifies the maximum time that the SAS target port is permitted to maintain a
connection without transferring a frame to the initiator port, specified in 100 microsecond increments. When this
value is exceeded, the target port will prepare to close the connection by transmitting DONE.A value of zero
indicates that there is no bus inactivity time limit.
- Disconnect Time Limit is not supported.
- Write Buffer Empty Ratio is the numerator of a fraction whose denominator is 256. The fraction indicates how
empty the drive data buffer should be before attempting to re-arbitrate for the link. If the ratio is set to 0h, the
target will calculate and use an optimal ratio based on the negotiated transfer rate. Both the Read Buffer Full
Ratio and the Write Buffer Empty Ratio pertain to the current active notch. For each active notch as defined in
page 0Ch there are separate Read Buffer Full Ratios and Write Buffer Empty Ratios. When the active notch is
set to zero, the values are applied in mode page 0Ch across all notches.
- Maximum Connect Time Limit specifies the maximum amount of time the drive will keep a SAS connection
open. The time is specified in 100 microsecond increments. The default value of zero indicates no time limit. A
maximum value of FFFFh specifies a connection time limit of 6.55 seconds. When this time expires, the drive
will prepare to close the connection.
- Maximum Burst Size field indicates the maximum amount of data that the target port shall transfer during a
single data transfer operation. This value is expressed in increments of 512 bytes. A value of zero specifies