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.

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