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The Ready LED Out signal is designed to pull down the cathode of an LED. The anode is attached to the proper +3.3 volt supply through
an appropriate current limiting resistor. The LED and the current limiting resistor are external to the drive. See Table 17 for the output
characteristics of the LED drive signals.
Table 17
LED drive signal
State
LED off, high
LED on, low
11.5.2
Differential signals
The drive SAS differential signals comply with the intra-enclosure (internal connector) requirements of the SAS standard.
Table 18 defines the general interface characteristics.
Table 18
General interface characteristics
Characteristic
Bit rate (nominal)
Unit interval (UI)(nominal)
Impedance (nominal, differential )
Transmitter transients, maximum
Receiver transients, maximum
11.6
SAS-2 Specification compliance
Seagate SAS-2 drives are entirely compatible with the latest SAS-2 Specification (T10/1760-D) Revision 16.
The most important characteristic of the SAS-2 drive at 6.0Gb/s is that the receiver is capable of adapting the equalizer to optimize the
receive margins. The SAS-2 drive has two types of equalizers:
1.
A Decision Feedback Equalizer (DFE) which utilizes the standard SAS-2 training pattern transmitted during the SNW-3 training gap.
The DFE circuit can derive an optimal equalization characteristic to compensate for many of the receive losses in the system.
2.
A Feed Forward Equalizer (FFE) optimized to provide balanced receive margins over a range of channels bounded by the best and
worst case channels as defined by the relevant ANSI standard.
11.7
Additional information
Please contact the Seagate representative for SAS electrical details, if required.
For more information about the Phy, Link, Transport, and Applications layers of the SAS interface, refer to the Seagate SAS Interface
Manual, part number 100293071.
For more information about the SCSI commands used by Seagate SAS drives, refer to the Seagate SCSI Commands Reference Manual,
part number 100293068.
S
E
P
EAGATE
NTERPRISE
ERFORMANCE
Test condition
0 V
VOH
3.6 V
I
= 15 mA
OL
Units
Mbaud
ps
ohm
V
V
15K HDD
5
T
V
AND
URBO
Output voltage
-100 μA < I
OH
0
V
0.225 V
OL
3.0 Gbps
6.0 Gbps
3000
6000
333.3
166.6
100
100
1.2
1.2
1.2
1.2
SSHD
2 P
M
, R
V
RODUCT
ANUAL
< 100 μA
12 Gbps
12000
83.3
100
1.2
1.2
. B
EV
55
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