There are three common physical layer (PHY) variants for multidrop single pair Ethernet (SPE), basic PHY, media access controller (MAC) PHY, and transceiver. They rely on different interfaces, including a media-independent interface (MII), reduced media-independent interface (RMII), serial peripheral interface (SPI), OPEN Alliance 3-pin (OA-3P), and Ethernet advanced physical layer (Ethernet-APL). This article begins with