Add Wired Ethernet to an MCU: SPI-to-Ethernet Selection Guide
Hardwired TCP/IP, SPI MAC+PHY, or an MCU with on-chip MAC — how to choose
There are three main ways to add wired Ethernet to an MCU: (1) a hardwired TCP/IP chip (stack on-chip — least MCU/firmware overhead), (2) an SPI MAC+PHY (you run a software stack, more flexible), or (3) an MCU with an on-chip Ethernet MAC plus an external PHY. Below are JLink-distributed parts and selection notes for each.
① Hardwired TCP/IP chips (least MCU overhead)
The TCP/IP stack lives on-chip; the MCU just moves data over SPI — ideal for resource-limited or fast-to-market designs.
The mainstream pick: 8 sockets, 32KB buffer, 80MHz SPI.
Low-power upgrade of the classic W5100.
Pick when you need IPv4/IPv6 dual-stack (pin-compatible with W5100S).
High throughput, parallel-bus interface.
② SPI MAC+PHY (software stack, more flexible)
MAC+PHY integrated, connected over SPI, paired with a software stack like lwIP — common on platforms such as ESP32.
10/100M, 16KB SRAM, checksum offload, with an ESP32 reference design.
The QFN-32 small-package variant of the DM9051.
③ MCU with on-chip Ethernet MAC + external PHY
If the MCU has a 10/100 MAC, you only add an external PHY — and you can source MCU and PHY from one supplier.
Cortex-M3 120MHz with an on-chip 10/100 Ethernet MAC.
The 10/100 PHY (MII/RMII) to pair with the MCU above.
Cross-references
Related guides
Frequently asked questions
W5500 or DM9051 — which should I choose? ▾
The W5500 has a hardwired TCP/IP stack — least MCU overhead, fastest to start; the DM9051 is an SPI MAC+PHY needing a software stack but more flexible, with an official ESP32 reference design. Pick W5500 for limited resources/fast start, DM9051 if you already use lwIP/ESP32.
ENC28J60 is short/EOL — what replaces it? ▾
Move to the W5500 (offloads the stack to the chip) or the DM9051 (a peer SPI MAC+PHY). Both are design-in alternatives — see the cross-reference pages.
Which part supports IPv6? ▾
The W6100 has a dual IPv4/IPv6 stack and is pin-compatible with the W5100S; for new designs needing long-term compatibility pick the W6100, or the QSPI-based W6300.
Not sure which part fits?
Tell us your application and constraints — our engineers will recommend a part and quote stock, pricing, and lead time.
Request a Quote