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PHY is an abbreviation for the physical layer of the OSI model.
An instantiation of PHY connects a link layer device (often called a MAC) to a physical medium such as an optical fiber or copper cable. A PHY device typically includes a Physical Coding Sublayer (PCS) and a Physical Medium Dependent (PMD) layer. The PCS encodes and decodes the data that is transmitted and received. The purpose of the encoding is to make it easier for the receiver to recover the signal.
An Ethernet physical transceiver is often called a PHYceiver. It is a device that operates at physical layer of OSI network model.
An Ethernet PHYceiver is a chip that implements the hardware send and receive function of Ethernet frames; it interfaces to the line modulation at one end and binary packet signaling at the other. Functions like MAC addressing are implemented by the Media Access Control function. Wake-on-LAN and Boot ROM functionality is implemented in the network interface card (NIC), which may have PHY, MAC and other functionality integrated into one chip or as separate chips.
100 Mbit/s and faster line speeds is implemented with a digital signal processor (DSP) inside the Ethernet PHY.
Some examples of Ethernet PHYceiver chips are Integrated Circuit Systems ICS1893, Realtek RTL8201 and VIA Technologies VIA6103.
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