# HCCA-SAFE: A Hybrid Cascaded Control Architecture for FPGA-Based Fault Injection in Safety-Critical Automotive SoCs

## TL;DR

The paper introduces HCCA-SAFE, a new FPGA-based fault injection architecture that improves timing and scalability for safety verification in automotive SoCs.

## Contribution

HCCA-SAFE is a novel hybrid cascaded control architecture that reduces net delay and control-signal fanout in FPGA-based fault injection for automotive SoCs.

## Key findings

- HCCA-SAFE reduces net delay by up to 63.8% compared to centralized fault injection methods.
- The architecture limits control-signal fanout significantly, improving FPGA resource utilization.
- Speed-up factors of up to 2123× are achieved on complex processor cores with HCCA-SAFE.

## Abstract

Automotive System-on-Chips (SoCs) must meet stringent functional safety standards, such as ISO 26262 and IEC 61508, to ensure reliable operation under hardware faults. FPGA-based fault injection has emerged as a practical and cost-effective technique for functional safety verification. However, instrumentation-based methods face scalability challenges when applied to the high fault densities typical of automotive SoCs. To address these challenges, we propose a hybrid cascaded fault-injection controller architecture (HCCA-SAFE) that simultaneously reduces high-fanout global nets and eliminates long serial propagation paths. The architecture constrains enable-signal cluster width and distributes control across cascaded stages, improving timing results and routability under limited FPGA resources. The proposed architecture is evaluated on multiple open-source RISC-V processor cores. On openE902, HCCA-SAFE reduces net delay from 27.276 ns to 22.535 ns and achieves 32.2% and 63.8% lower net delay compared with the representative centralized and shift-chain approaches, respectively. On openE906, the proposed HCCA-SAFE limits the net delay to 12.959 ns and reduces the maximum control-signal fanout to 1763, respectively, compared with 25.825 ns and 40.442 ns in the conventional method. On openC906, the proposed design lowers the maximum control-signal fanout from 7725 to 570 and reduces the net delay to 7.506 ns. Furthermore, HCCA-SAFE produces results fully consistent with software-based RTL simulation, while delivering substantial performance gains. Speed-up factors of 127×, 206×, and 2123× are achieved on openE902, openE906, and openC906, respectively, with efficiency improvements scaling with processor complexity These results confirm that HCCA-SAFE delivers scalable, timing-robust fault-injection control suitable for large automotive SoCs.