This week, I’m attending NXP’s Analyst Summit in Silicon Valley, where the company announced the MCX A5 microcontroller family. The big news is the network. NXP says this is the first microcontroller to combine a 10BASE-T1S Ethernet interface with automatic network topology discovery and post-quantum cryptography. This combination gives factories, commercial buildings, and energy infrastructure a route to standard IP networking over single-pair wiring.
The chip has an Arm Cortex-M33 core running up to 240 MHz with up to 2 MB of flash and 640 KB of RAM, and a full set of features — UART, I²C, I3C, SPI, CAN FD, high-speed USB, FlexIO, PSA Certified Level 3 security, and a post-quantum hardware root of trust. Post-quantum is important in industrial applications because equipment tends to remain in service for a decade or two. The MCUXpresso SDK ships with long-term support releases, and the family supports Zephyr RTOS. Parts are sampling now.
Why IP Is Important
Internet Protocol is the foundation beneath the networks we use every day. IP packets travel over wired and wireless networks such as Ethernet, Wi-Fi, cellular, or Thread. Although IP networks have forty years of standardization and global deployment, many industrial systems still use pre-IP connectivity. Most sensors, actuators, and controllers on plant floors still communicate over RS-485, an electrical signaling standard published in 1983, or RS-232, which is older still. RS-485 survived because it’s simple and it works. Two wires, dozens of devices tapped along the same cable, long runs, high noise immunity, low cost, deterministic behavior. However, RS-485 is not an IP network, so each vendor layered a proprietary protocol on top of it, trapping data in isolated ecosystems.
Why didn’t industrial applications follow the herd to IP networking? One reason is industry inertia — what we have is “good enough” — and the other is wiring. Modern Ethernet requires two or four pairs of wires. There’s no multi-tap capability, so each device needs its own wire back to a switch. RS-485 is single-pair, so migrating to Ethernet requires pulling a dedicated cable to every endpoint and installing switch ports to terminate them. Plant operators did the math and declined.
10BASE-T1S
10BASE-T1S, standardized as IEEE 802.3cg in 2019, runs 10 Mbps Ethernet over a single pair of wires with multiple nodes tapped along the same cable. The protocol stack is IP, as in other modern networks. One wire pair, devices strung along the bus, no switch, just like RS-485. The wiring topology is essentially the same, within limits: 802.3cg guarantees only 25 meters for a multidrop segment (RS-485 is 1,200 meters). I’ll talk about the 10BASE-T1L, the kilometer-range variant, in a future post. 10BASE-T1S isn’t a plug-and-play retrofit, but the topology is right, and it’s a great option for upgrading serial connections to IP.
Control systems require a guaranteed response time, and classic Ethernet cannot give one. Nodes transmit whenever the wire looks idle and sort out collisions later, so latency is variable. IEEE 802.3cg adds Physical Layer Collision Avoidance, which gives each node a scheduled turn in a repeating sequence. Collisions do not occur, and latency has an upper bound that engineers can calculate.
None of this is speculative. Automotive adopted 10BASE-T1S first, where wiring harness weight and volume are direct cost, and the standard is now supported by parts from NXP, Microchip, Analog Devices, onsemi, and TI, with OEM zonal-architecture programs reaching production. Industrial installations inherit a proven, hardened technology.
Topology Discovery
An Ethernet switch knows which device is connected to each port. A multidrop bus has one port for everything on the cable, so it has no such map. Sixteen identical temperature sensors on a single wire run are electrically indistinguishable, and the one reporting a fault could be any of them. 10BASE-T1S topology discovery, as specified by the OPEN Alliance, measures the signal propagation delay between nodes and converts it into the physical distance along the cable. The result is an ordered map of what is on the bus and where. Automating topology discovery replaces manual, error-prone tracing and labeling.
My Take
The MCX A5 is a big step forward in industrial networking. Charles Dachs, who runs NXP’s Secure Connected Edge business, framed the forcing function correctly in the announcement: industrial edge AI cannot deliver its benefits without access to real-time data, and most of that data remains stranded behind serial links. AI is what finally makes upgrading plant networks worth paying for, and 10BASE-T1S makes it affordable.
Of course, adoption will take a while. The enormous “brownfield” installed base of legacy equipment will sit alongside new IP-connected equipment for many years to come, so we’ll have a mix of industrial networks for the foreseeable future. But the upgrade path is now clear, and it begins with new, intelligent systems that have IP networking from the start. NXP is in a leadership position as this transition begins.
