10BASE-T1S Physical Layer Architecture

The primary purpose of 10BASE-T1S is to provide a network similar in cost with the advantages of multi-drop topology to legacy in-vehicle networks such as CAN/CAN-FD and FlexRay. Due to this, many aspects of the physical layer implementation are very different from most of the other forms of Ethernet covered in this chapter. It should be noted that 10BASE-T1S supports not only multi-drop topology but also point-to-point. In point-to-point mode, full-duplex is supported, and auto-negotiation is optional.

Practical Physical Implementations

The standard interface to hosts defined by IEEE is xMII. The Reduced Medium Independent  Interface (RMII) has a pin count of 10 pins. By comparison, most CAN-FD and FlexRay implementations have a smaller pin count. Reduced pin count has large advantages due to the expense of physical PCB real estate. To compete with these legacy networks, several alternative PHY interfaces are proposed, including:

• MAC PHY: Open Alliance has proposed in TC6 a SPI interface with a pin count of 5.
• Integrated PHY: A PHY or multiple PHYs can be integrated directly into a System-on-Chip (SoC) so that the entire implementation is inside one chip.
• Transceiver PHY: In this implementation, the analog system is separated from the digital section, similar to widely available CAN-FD transceivers. Open Alliance has defined a standard analog interface with a pin count of 3.

4 possible physical implementations. Non xMII alternatives are proposed in order to be similar in pin-count, size and costs to CAN-FD and FlexRay implementations.

Intrepid’s 10BASE-T1S Hardware