The VSC056 device is an I/O-intensive peripheral device that is intended to be part of a cost-effective Fibre Channel Arbitrated Loop (FC-AL), Small Computer System Interface (SCSI), Serial Attached SCSI (SAS), or Serial ATA (SATA) enclosure management solution. The device contains an address-programmable two-wire serial interface, a block of control and status registers, I/O port control logic, specialized port bypass control logic, and a clockgeneration block. Along with an external crystal, the device can be configured to support up to 64 bits of general-purpose I/O; or 16 bits of general-purpose I/O, 32 bits of port bypass control (16 pairs supporting 16 drives), eight fan speed monitoring inputs, and eight pulse-width modulated general-purpose control outputs. The VSC056 supports various combinations of individual port bypass circuit (PBC), clock recovery unit (CRU), and signal detect unit (SDU) functions, as well as integrated solutions. The control register portion of the device allows the user to individually program each I/O pin as an input, an output, or an open-drain or open-source output.