Low-Cost Industrial Ethernet with GD32’s Integrated MAC + a DAVICOM PHY (GD32F207 / F407 + DM9161A / DM9162)
GD32F207 / GD32F407 integrate a 10/100 Ethernet MAC; add a DAVICOM DM9161A / DM9162 PHY over MII or RMII to build low-cost industrial Ethernet. This guide clarifies which GD32 parts actually have the MAC, how the MAC connects to a PHY, and the real difference between DM9161A and DM9162.
Which GD32 parts have the Ethernet MAC? (F405 does not!)
GD32F207 (Cortex-M3, 120MHz) and GD32F407 (Cortex-M4, 168MHz, with FPU) both integrate one IEEE 802.3-compliant 10/100 Mbps Ethernet MAC, with a dedicated DMA and SRAM and IEEE 1588 PTP support; both use the same MAC IP, differing in core performance. Watch one common misconception: not every GD32F4 has Ethernet — for example the GD32F405, though also an M4 at 168MHz, has no Ethernet MAC (and no camera interface); for an integrated MAC, specify the GD32F407 (or the larger F427/F450/F470). Always confirm the Ethernet field on each part’s datasheet when selecting.
How the MAC connects to an external PHY: MII vs RMII
The GD32 MAC connects to an external PHY over MII or RMII. MII uses about 16 signals with two 25MHz TX/RX clocks supplied by the PHY; RMII reduces this to about 7 signals using a single shared 50MHz reference clock (REF_CLK), saving pins and suiting pin-constrained packages. In either mode the MAC uses the MDC/MDIO (IEEE 802.3 clause-22) two-wire management interface to read and write the PHY’s standard registers (such as BMCR and BMSR) for speed/duplex/auto-negotiation. The most common RMII pitfall is the 50MHz reference clock: it must keep the MAC and PHY in the same clock domain, supplied either by an external oscillator to both or output by the PHY (the DM9162 lists an RMII 50MHz clock output).
DM9161A vs DM9162: both do MII/RMII — the difference is temperature grade
A frequently mis-stated point: both the DM9161A and DM9162 support MII and RMII (selectable) — the DM9161A is not MII-only. Per DAVICOM’s own datasheets, both comply with IEEE 802.3/802.3u 10/100, both have auto-negotiation and Auto-MDIX, both use the clause-22 MDC/MDIO management interface, and both run on a single 3.3V supply. The real difference is that the DM9162 is the industrial-temperature (−40~85°C) part, offers more packages (LQFP-48, QFN-32 and more), and is pin-to-pin compatible with the DM9161A/C in LQFP-48 — DAVICOM’s successor to / replacement for the DM9161C. So for longevity and industrial temperature, choose the DM9162; an existing DM9161A design can also migrate smoothly.
Why the combination is cost-effective, plus design notes
When the MCU already integrates a MAC (GD32F207/F407), you only add a cheap PHY (DM9161A/DM9162) plus Ethernet magnetics and an RJ45 to reach 100Mbps Ethernet — and it can fill the bandwidth better than “an MCU without a MAC plus an SPI-interface MAC+PHY (such as DAVICOM DM9051),” because an SPI interface is throughput-limited by the SPI clock whereas MII/RMII is a parallel bus. Conversely, if your MCU has no MAC (e.g. GD32F405 or a small M0/M3), an SPI MAC+PHY like the DM9051 is the pin-saving, easy-to-integrate choice instead. Design notes: keep the RMII 50MHz reference clock single-source and route it as a controlled-impedance, length-matched net; place Ethernet magnetics between the PHY and RJ45 (or use a MagJack with built-in magnetics); the GD32 and DAVICOM PHY are both 3.3V I/O, so no level shifting is needed.
Products mentioned
GD32F207 Cortex-M3 MCU with Ethernet MAC
The GD32F207 is a high-performance 32-bit Arm Cortex-M3 MCU from GigaDevice at 120MHz, with up to 3072KB flash / 256KB SRAM and an integrated 10/100 Ethernet MAC (with IEEE 1588) — pair it with an external Ethernet PHY (e.g. DAVICOM DM9161A/DM9162) for wired networking. It also offers USB 2.0 FS (OTG), dual CAN 2.0B, up to three 12-bit ADCs and two DACs; larger SKUs add a TFT-LCD interface (TLI), camera interface (DCI), and AES/HASH/TRNG security. At 2.6~3.6V in LQFP64~176, it suits industrial gateways, HMI, and networking gear.
GD32F407 Arm Cortex-M4 High-Performance MCU
The GD32F407 is a high-performance 32-bit MCU from GigaDevice with an Arm Cortex-M4 core (FPU/DSP) at 168MHz, up to 1MB Flash and 192KB SRAM, integrating USB OTG (FS+HS), 10/100 Ethernet MAC, and CAN. With packages aligned to the STM32F407 (LQFP100/144), it is commonly used as an STM32F407-class alternative.
DM9162 10/100M Ethernet PHY Transceiver
The DM9162 is a DAVICOM 10/100Mbps single-port Fast Ethernet PHY transceiver compliant with IEEE 802.3/802.3u, offering an MII/RMII MAC interface, HP Auto-MDIX, and auto-negotiation. A single 3.3V supply with 5V-tolerant I/O in a 48-pin LQFP / 32-pin QFN — commonly paired with MCUs/SoCs that expose an MII/RMII MAC.
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