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| 1 | +--- |
| 2 | +title: Implement safety-critical isolation using safety island architecture |
| 3 | +weight: 5 |
| 4 | + |
| 5 | +### FIXED, DO NOT MODIFY |
| 6 | +layout: learningpathall |
| 7 | +--- |
| 8 | +## How safety islands support functional safety |
| 9 | + |
| 10 | +In automotive systems, a non-safety ECU (Electronic Control Unit) typically runs non-critical tasks such as infotainment or navigation. A safety island, by contrast, is dedicated to executing safety-critical control logic (for example, braking and steering) with strong isolation, redundancy, and determinism. |
| 11 | + |
| 12 | +The table below compares the characteristics of an ECU and a safety island in terms of their role in supporting functional safety. |
| 13 | + |
| 14 | +| Feature | ECU | Safety island | |
| 15 | +|------------------------|----------------------------|--------------------------------------| |
| 16 | +| Purpose | Comfort/non-safety logic | Safety-critical decision making | |
| 17 | +| OS/runtime | Linux, Android | RTOS, hypervisor, or bare-metal | |
| 18 | +| Isolation | Soft partitioning | Hardware-enforced isolation | |
| 19 | +| Functional safety requirement | None to moderate | ISO 26262 ASIL-B to ASIL-D compliant | |
| 20 | +| Fault handling | Best-effort recovery | Deterministic safe-state response | |
| 21 | + |
| 22 | +This comparison shows why safety-critical software depends on dedicated hardware domains to meet functional safety goals. |
| 23 | + |
| 24 | +If the main processor fails or becomes inoperable, a safety island can take over critical safety functions such as deceleration, stopping, and fault handling to prevent catastrophic system failures. |
| 25 | + |
| 26 | +{{% notice Tip %}} |
| 27 | +Safety islands are often implemented as lockstep cores or separate MCUs that run on real-time operating systems (RTOS), offering guaranteed performance under fault conditions. |
| 28 | +{{% /notice %}} |
| 29 | + |
| 30 | +## Key capabilities of a safety island |
| 31 | +- **System health monitoring** continuously monitors the operational status of the main processor (for example, the ADAS control unit) and detects potential errors or anomalies |
| 32 | +- **Fault detection and isolation** independently detects failures and initiates emergency handling for overheating, execution faults, or unresponsiveness |
| 33 | +- **Essential safety functions conitnue to operate**, even if the main system crashes. A safety island can execute fallback operations, such as: |
| 34 | + - Autonomous Vehicles → safe stopping (fail-safe mode) |
| 35 | + - Industrial Equipment → emergency power cutoff or speed reduction |
| 36 | + |
| 37 | +## Why a safety island matters for functional safety |
| 38 | + |
| 39 | +A safety island provides a dedicated environment for executing critical safety functions. Its key characteristics include: |
| 40 | + |
| 41 | +- **Acting as an independent redundant safety layer** |
| 42 | + - Operates safety logic independently of the main processor |
| 43 | + |
| 44 | +- **Supporting the ASIL-D safety level** |
| 45 | + - Enables the system to meet the highest ISO 26262 requirements for critical operations |
| 46 | + |
| 47 | +- **Providing independent fault detection and recovery mechanisms:** |
| 48 | + - *Fail-safe*: activating a minimal-risk mode, such as limiting vehicle speed or switching to manual control |
| 49 | + - *Fail-operational*: allowing high-integrity systems, such as those in aerospace or autonomous driving, to continue functioning under fault conditions |
| 50 | + |
| 51 | +Safety islands play a key role in enabling ISO 26262 compliance by isolating safety-critical logic from general-purpose processing. They're a proven solution for improving system determinism, fault tolerance, and fallback behavior. |
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