Revision 4.2
July 29, 2005
VSC7177 Data Sheet
Enhanced 2:1 Port Selector for Serial ATA and Serial Attached SCSI
FEATURES
● 2:1 port selector for both Serial ATA (SATA) and
Serial Attached SCSI (SAS) links
● Serial ATA 1.0 compliant at 1.5 Gbps
(3.0 Gbps capable)
● Sideband port selection
● Complies with Serial ATA II: Port Selector
specification 1.0, including failover control
● Passes Serial ATA patterns transparently
● Programmable receiver sensitivity
● High output swing mode with pre-emphasis
● Compatible with legacy designs (VSC7173 and
VSC7175); provides enhanced connectivity and
signal pre-emphasis
● 0.6 W to 0.8 W power dissipation (depending on
operating mode)
● 3.3 V power supply
● 32-pin, 7 mm x 7 mm QFP-N package
APPLICATIONS
● Active-passive redundant failover systems
● Dual-port Serial ATA and Serial Attached SCSI
disk arrays (JBODs)
● NAS servers
● RAID subsystems
● Disk-based backup systems
● Serial ATA and Serial Attached SCSI routing
applications
● Buffers for externally connected links
To order the VSC7177 device, see “Ordering Information,” page 24.
GENERAL DESCRIPTION
The VSC7177 is a Serial ATA and Serial Attached SCSI multiplier/buffer that implements a 2:1 port selector
function for 1.5 Gbps and 3.0 Gbps links. This function is used when dual hosts, such as I/O controllers, must access
single-port disk drives in high availability storage subsystems where redundancy and load sharing are important. The
outputs from the I/O controllers are muxed to a Serial ATA or Serial Attached SCSI drive. The output from the
Serial ATA drive is buffered and replicated to the I/O controllers. When switching from one I/O controller to the
other, a Serial ATA link must be re-initialized with out-of-band (OOB) signals, which are transferred through the
VSC7177 transparently. The VSC7177 provides high output swings, pre-emphasis, and programmable receiver
sensitivity that are needed to drive long backplanes and external cables.
Port connectivity for the device can be configured using driving external I/O pins or through protocol-based port. See
the block diagram on page 2.
Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
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