WalkaboutWiFi.com: Arduino Ethernet R3 A000068 Posted in: Specs | by Brian Taylor | 2016 Sept 11
The Arduino Ethernet is a microcontroller board based on the ATmega328 (datasheet). It has 14 digital input/output pins, 6 analog inputs, a 16 MHz crystal oscillator, a RJ45 connection, a power jack, an ICSP header, and a reset button.
An optional Power over Ethernet module can be added to the board as well.
NB: Pins 10, 11, 12 and 13 are reserved for interfacing with the Ethernet module and should not be used otherwise. This reduces the number of available pins to 9, with 4 available as PWM outputs.
The Ethernet differs from other boards in that it does not have an onboard USB-to-serial driver chip, but has a Wiznet Ethernet interface. This is the same interface found on the Ethernet shield.
An onboard microSD card reader, which can be used to store files for serving over the network, is accessible through the SD Library. Pin 10 is reserved for the Wiznet interface, SS for the SD card is on Pin 4.