ENC28J60 — Standalone Ethernet Controller with SPI Interface

Overview

The ENC28J60 is a standalone 10BASE-T Ethernet controller manufactured by Microchip Technology. Packaged as a 28-pin IC or a compact PCB breakout module equipped with an integrated HR911105A RJ45 MagJack connector (with internal isolation magnetics and status LEDs), it enables microcontrollers to connect to wired LAN networks over an SPI interface.

Integrating a fully compliant IEEE 802.3 MAC (Media Access Control) layer, 10 Mbps physical layer transceiver (PHY), programmable hardware packet filtering, and an 8 KB dual-port RAM transmit/receive buffer, the ENC28J60 is a classic hardware solution for adding wired Ethernet connectivity to Arduino Uno, ESP32, STM32, and Raspberry Pi Zero projects.

Quick reference


Operating voltage (`VCC`)	3.3 V to 5.0 V DC (breakout module with 3.3V LDO)
IC supply voltage (`VDD`)	3.1 V to 3.6 V DC (3.3 V nominal)
Ethernet standard	IEEE 802.3 10BASE-T (10 Mbps half/full duplex)
Interface	SPI (up to 20 MHz)
Internal packet buffer	8 KB dual-port SRAM (transmit and receive FIFO)
I/O tolerance	5V tolerant SPI inputs (`CS`, `SCK`, `SI`)
Connector	RJ45 MagJack with built-in isolation transformer & status LEDs
Operating current	$160\text{ mA}$ typical transmit / $2\ \mu\text{A}$ standby

Pinout

Standard 10-pin or 12-pin double-row 0.1" (2.54 mm) breakout module header:

Pin	Name	Type	Description
1	`VCC` / `3.3V`	Power	Power supply input (+3.3 V to +5.0 V DC)
2	`GND`	Power	Ground reference (0 V)
3	`CS` / `SS`	Digital Input	Active-Low SPI Chip Select
4	`SCK` / `CLK`	Digital Input	SPI Serial Clock
5	`SI` / `MOSI`	Digital Input	SPI Serial Data Input
6	`SO` / `MISO`	Digital Output	SPI Serial Data Output
7	`WOL`	Digital Output	Wake-On-LAN signal output (optional)
8	`INT`	Digital Output	Active-Low interrupt output pin
9	`RST` / `RESET`	Digital Input	Active-Low hardware reset pin
10	`CLKOUT`	Digital Output	Programmable clock output pin (default 6.25 MHz)

Specifications

Parameter	Symbol	Min	Typ	Max	Unit	Conditions
Supply Voltage (Module)	$V_{CC}$	3.3	3.3 / 5.0	5.5	V	Power rail with 3.3V LDO
Transmit Current	$I_{tx}$	—	160	180	mA	10BASE-T active transmission
Receive Current	$I_{rx}$	—	120	140	mA	Receiving Ethernet packets
SPI Clock Frequency	$f_{SPI}$	0	14	20	MHz	SPI Mode 0,0 ( $CPOL=0, CPHA=0$ )
SRAM Buffer Memory	$RAM$	—	8192	—	Bytes	Configurable Rx/Tx buffer split
Transmission Speed	$Speed$	—	10	—	Mbps	10BASE-T Ethernet

Software Architecture & Software TCP/IP Stack

Unlike the WIZnet W5500 (which features a hardware-implemented TCP/IP stack on chip), the ENC28J60 handles only Layer 1 (PHY) and Layer 2 (MAC) Ethernet frames in hardware:

Ethernet Packet Buffering: Incoming Ethernet frames are stored in the 8 KB internal SRAM buffer.
Software TCP/IP Stack: The host microcontroller (Arduino/ESP32) must run a software TCP/IP stack—such as UIP, EtherCard, or EthernetENC—to process IP, ARP, ICMP (ping), UDP, and TCP packets.

Wiring

ENC28J60 Pin	Arduino Uno	ESP32	Notes
`VCC` / `3.3V`	3.3V / 5V	3.3V	Requires up to 180 mA current
`GND`	GND	GND	System ground
`SCK`	Digital D13	GPIO 18	SPI Clock
`SO` (MISO)	Digital D12	GPIO 19	SPI MISO
`SI` (MOSI)	Digital D11	GPIO 23	SPI MOSI
`CS`	Digital D10	GPIO 5	SPI Chip Select
`RESET`	Digital D8	GPIO 16	Hardware Reset (optional)

Warning

High Current Supply Hazard:

The ENC28J60 draws up to 180 mA during Ethernet frame transmission. Connecting VCC to weak 3.3V regulator pins (such as the 3.3V pin on old FTDI USB-to-serial adapters or early Arduino boards) causes voltage dips and connection resets. Always connect to a high-current 3.3V rail capable of $\ge 250\text{ mA}$ .

Example (Arduino `EthernetENC` Web Server)

cpp

#include <SPI.h>
#include <EthernetENC.h>

// MAC address for controller
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
IPAddress ip(192, 168, 1, 177);

EthernetServer server(80);

void setup() {
  Serial.begin(9600);
  
  // Initialize Ethernet with Chip Select pin 10
  Ethernet.init(10);
  Ethernet.begin(mac, ip);

  server.begin();
  Serial.print("ENC28J60 Web Server online at IP: ");
  Serial.println(Ethernet.localIP());
}

void loop() {
  EthernetClient client = server.available();
  if (client) {
    Serial.println("New HTTP client connected");
    boolean currentLineIsBlank = true;

    while (client.connected()) {
      if (client.available()) {
        char c = client.read();
        if (c == '\n' && currentLineIsBlank) {
          // Send HTTP response header
          client.println("HTTP/1.1 200 OK");
          client.println("Content-Type: text/html");
          client.println("Connection: close");
          client.println();
          client.println("<!DOCTYPE HTML>");
          client.println("<html><h1>VoltDocs ENC28J60 Ethernet Server</h1></html>");
          break;
        }
        if (c == '\n') {
          currentLineIsBlank = true;
        } else if (c != '\r') {
          currentLineIsBlank = false;
        }
      }
    }
    delay(1);
    client.stop();
  }
}

Common mistakes

Powering from weak 3.3V sources: Under-powering the module causes network dropouts or inability to establish a link with network switches.
Conflating ENC28J60 and W5500 libraries: ENC28J60 requires libraries like EthernetENC or EtherCard; standard W5500 Ethernet.h libraries will fail to initialize the chip.

Notes

ENC28J60 vs W5500: ENC28J60 is 10 Mbps and requires a software TCP/IP stack; W5500 is 100 Mbps and implements a full hardware TCP/IP stack offloading MCU RAM.