The Arduino Ethernet Shield v2 allows an Arduino board to connect to the internet. It is based on the Wiznet W5500 ethernet chip. The Wiznet W5500 provides a network (IP) stack capable of both TCP and UDP. It supports up to eight simultaneous socket connections. Use the Ethernet library to write sketches which connect to the internet using the shield.
The Ethernet Shield v2 connects to an Arduino board using long wire-wrap headers which extend through the shield. This keeps the pin layout intact and allows another shield to be stacked on top..
The most recent revision of the board exposes the 1.0 pinout on rev 3 of the Arduino UNO Board.
The Ethernet Shield v2 has a standard RJ-45 connection, with an integrated line transformer and Power over Ethernet enabled.
There is an onboard micro-SD card slot, which can be used to store files for serving over the network. It is compatible with the Arduino Uno and Mega (using the Ethernet library). The onboard micro-SD card reader is accessible through the SD Library. When working with this library, SS is on Pin 4.
The Shield also includes a reset controller, to ensure that the W5500 Ethernet module is properly reset on power-up. Previous revisions of the Shield were not compatible with the Mega and needed to be manually reset after power-up.
Arduino communicates with both the W5500 and SD card using the SPI bus (through the ICSP header). This is on digital pins 10, 11, 12, and 13 on the Uno and pins 50, 51, and 52 on the Mega. On both boards, pin 10 is used to select the W5500 and pin 4 for the SD card. These pins cannot be used for general I/O. On the Mega, the hardware SS pin, 53, is not used to select either the W5500 or the SD card, but it must be kept as an output or the SPI interface won't work.
Note that because the W5500 and SD card share the SPI bus, only one at a time can be active. If you are using both peripherals in your program, this should be taken care of by the corresponding libraries. If you're not using one of the peripherals in your program, however, you'll need to explicitly deselect it. To do this with the SD card, set pin 4 as an output and write a high to it. For the W5500, set digital pin 10 as a high output.
The Shield provides a standard RJ45 Ethernet jack.
The reset button on the Shield resets both the W5500 and the Arduino Board.
Note: The Ethernet Shield 2 is, at present time, not compatible with the Arduino Zero Pro Board.