New SiFive CPUs Hit the Road

SiFive has entered the automotive market, offering small embedded and application cores for ASIL B and ASIL D systems.

Bryon Moyer

SiFive, in its first automotive foray, has upgraded three of its licensable RISC-V CPUs for that market, including two devices from the Essential family and one from the Intelligence family. Different models target ASIL B or ASIL D safety levels.

The E6-A and X280-A come in versions that support dual-core-lockstep (DCLS), split-lock, and non-DCLS configurations. The lone S7-A is a DCLS device. Each new part implements RTL modifications relative to its nonautomotive cousin, and all have the documentation and certification necessary for customers to certify chips and systems that employ them. The E6-A cores are available for licensing now, the X280-A cores are scheduled for availability in 2023, and the S7-A is set to arrive in 2024.

The evolving automotive architecture is moving away from electronic control units (ECUs) and toward domains or zones. Functions that a single microcontroller with a small core once handled are coming together in systems-on-a-chip (SoCs) with larger cores. Small designs such as the E6 are unlikely to serve as primary CPUs, but they can support safety or security. The X280, as an application-level CPU, can act as a prime core in such an SoC.

Intellectual-property (IP) cores, chips, and systems intended for automotive use must meet the functional-safety requirements of the ISO 26262 standard. Depending on the safety requirements, hardware changes may be necessary; in SiFive’s case, all the new cores are different in small but important ways from their nonautomotive counterparts.

In addition, the standard lays out specific certification and documentation requirements for automotive systems. That process is much easier if the system components come with their own documentation and precertification.