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CHEETAH 15K.7 SAS PRODUCT MANUAL, REV. F 52
11.5.2 Differential signals
The drive SAS differential signals comply with the intra-enclosure (internal connector) requirements of the SAS standard.
Table 16 defines the general interface characteristics.
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 Gbps 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 your 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.
Table 15 LED drive signal
STATE TEST CONDITION OUTPUT VOLTAGE
LED off, high 0 V ≤ VOH ≤ 3.6 V -100 μA < I
OH
< 100 μA
LED on, low I
OL
= 15 mA 0 ≤ V
OL
≤ 0.225 V
Table 16 General interface characteristics
CHARACTERISTIC UNITS 1.5 GBPS 3.0 GBPS 6.0 GBPS
Bit rate (nominal) Mbaud 1,500 3,000 6,000
Unit interval (UI)(nominal) ps 666.6 333.3 166.6
Impedance (nominal, differential ) ohm 100 100 100
Transmitter transients, maximum V ± 1.2 ± 1.2 ± 1.2
Receiver transients, maximum V ± 1.2 ± 1.2 ± 1.2