The shield version integrates a micro SD card slot, which can be used to store files for network serving. The Arduino Ethernet Shield is compatible with Arduino Uno and Mega (using the Ethernet Library). You can access the card slot on the board and use the SD library included in the available library set in the Arduino IDE.
The W5100 controller IC on the Arduino Ethernet Shield can transmit data using 2 protocols: TCP and UDP. The maximum number of simultaneous data transmission channels is 4. This is the strength of the W5100 compared to the Microchip ENC28J60. The ability to transmit 4 data streams simultaneously helps the board receive data from the internet with a lower error rate (usually caused by data loss on the transmission path or exceeding the time limit – time out).
SPECIFICATIONS
To use, you must have an accompanying Arduino board.
Operates at 5V voltage (supplied from the Arduino board)
Ethernet chip: W5100 with 16K internal buffer
Connection speed: 10/100Mb
Connects to the Arduino board via the SPI port
Libraries and sample code are available in the Arduino program.
Note: Because the W5100 and SD card use the same SPI transmission standard, only one device can be operated at a time. If you are using both peripherals in your program, this needs to be handled by the corresponding libraries.