Ethernet TSN

TSN (Time-Sensitive Networking) is a set of IEEE 802.1 standards that turn Ethernet into a link with time in the contract, not only best-effort delivery. Several industrial MCUs, including the STM32N6 series, integrate a Gigabit MAC with TSN.

What is wrong with ordinary Ethernet

Classic switched Ethernet is excellent at moving bulk data. It does not promise when a given frame will leave the port. A camera packet and a firmware-update packet compete. In a machine, a drive command that arrives 2 ms late is a different product than a web page that arrives 2 ms late.

What TSN adds

The parts you actually meet on an MCU:

• Time sync (802.1AS / gPTP) — a shared clock across the network
• Scheduled traffic (802.1Qbv) — gates on the transmitter so a class of frames gets a slot
• Priority and filtering (802.1Q) — not new, but required for the schedule to mean anything
• Pre-emption (802.1Qbu / 802.3br) — a large frame can be interrupted by a time-critical one

Together they let you say: this 64-byte cyclic frame goes out every 500 µs, and the rest of the traffic fills the gaps.

What it is not

TSN is not a fieldbus on its own. EtherCAT, PROFINET IRT, and OPC UA PubSub use TSN or sit beside it. You still need a stack, a profile, and a switch that speaks the same standards. A “TSN MAC” on the MCU is the hardware hook, not a turnkey PLC network.

On a board

The MAC is in the silicon. A PHY, magnetics, and an RJ45 (or a connector to a carrier) are board choices. If the product only needs a camera and USB, the TSN MAC can stay unused.

MAC addresses on STM32N6 live in OTP until you programme them. They are not printed in the factory.