PHY

PHY (often pronounced "fī.", IPA: [faɪ]) is a common abbreviation for physical layer of OSI model.

PHY is also a generic electronics term referring to a special electronic integrated circuit or functional block of a circuit that takes care of encoding and decoding between a pure digital domain (on-off) and a modulation in the analog domain. Often used to interface a field-programmable gate array (FPGA) or Complex Programmable Logic Device (CPLD) to a specific type of interface.

[edit] Example uses

A PHY chip (called PHYceiver) is commonly found on Ethernet devices. Its purpose is digital access of the modulated link. Usually used together with an MII-chip.
A PHY part is integrated into most Universal Serial Bus (USB) controllers in hosts or embedded systems and provides the bridge between the digital and modulated parts of the interface.
The Infrared Data Associations IrDA specification includes an IrPHY specification for the physical layer of the data transport.
Serial ATA controllers like the VIA6421 have a PHY.