Our client, a Tier-1 automotive OEM, operates a portfolio of ECUs for engine management, braking, and safety systems on the SH2A platform. As demand for better performance grew and the ISO 26262 ASIL-D standards became more rigorous, the platform had to adapt to keep pace with the next stage of their vehicle.
Our embedded mobility expert team executed a testing automotive Micro Controller Unit (MCU) firmware migration from SH2A (HEW compiler) to the RH850 platform (GHS compiler), achieving higher performance, scalability, and full functional safety alignment while preserving system behaviour in production.
Business Goals
The key objectives were:
- Migrate firmware from SH2A to RH850 with no behavioural deviation.
- Preserve deterministic real-time response metrics.
- Leverage RH850’s multi-core architecture and ≥200 MHz clock speed.
- Expand memory from less than 1 MB Flash / 64 KB RAM to 16 MB Flash / 2 MB RAM.
- Achieve ISO 26262 ASIL-D compliance.
- Reduce power consumption through dynamic voltage scaling.
- Establish a reusable migration framework for future microcontroller programs.
Our Solution
Firmware Migration & Compiler Transition
The full firmware stack was migrated from the HEW toolchain to the GHS compiler while preserving application logic.
Key actions included:
- Redesigning memory layouts to utilize RH850’s extended RAM and Flash
- Tuning optimization flags
- Validating interrupt routines and scheduling logic
- Verifying instruction-level compatibility and timing behaviour
Hardware Enablement & Peripheral Integration
To activate RH850 platform capabilities:
- Hardware Abstraction Layers were updated.
- Peripheral drivers were updated for Ethernet, CAN, ADC/DAC
- Clock trees were optimised, and pin functions were realigned.
- Low-level register mapping was revalidated to ensure deterministic access.
Automated Equivalence Testing Framework
We leveraged a comprehensive testing framework that validated behavioural equivalence by executing identical inputs on both platforms and verifying:
- Functional correctness
- Runtime performance consistency
- Regression avoidance
- Boundary and edge-case reliability
This ensures identical behaviour at every operational level prior to production approval.
Functional Safety Integration
To meet ISO 26262 ASIL-D requirements, we implemented and validated:
- Watchdog supervision
- Fault-tolerant execution paths
- Safety monitoring and fallback handling
All these safety functions were tested with planned fault simulations and recovered to the ideal state under safer and predictable conditions.
Key Highlights
Zero-Deviation Migration
Maintained exact behavioural equivalence across engine, braking, and safety ECUs throughout the SH2A to RH850 transition.
High-Performance Enablement
Enabled ≥200 MHz multi-core processing for improved real-time performance and deterministic execution.
ISO 26262 ASIL-D Compliance
Achieved the highest automotive safety classification through fault-tolerant architecture and safety monitoring mechanisms.
Advanced Peripheral Integration
Enabled Ethernet, CAN, and ADC/DAC to support next-generation vehicle functions.
Memory & Power Optimisation
Expanded to 16 MB Flash and 2 MB RAM while reducing power usage through dynamic voltage scaling.
Reusable Migration Framework
Created a standardized process for future Microcontroller transitions.
Platform Evolution: Before vs After Equivalence Testing
| Feature | Before Migration (SH2A) | After Migration (RH850) |
|---|---|---|
| Microcontroller | SH2A (16/32-bit RISC) | RH850 (32/64-bit multi-core) |
| Clock Speed | ~100 MHz | ≥200 MHz |
| Memory | <1 MB Flash, 64 KB RAM | 16 MB Flash, 2 MB RAM |
| Compiler | HEW | GHS |
| Compiler Optimisation | Platform-specific | Platform-specific |
| Peripherals | UART, timers, PWM | Ethernet, CAN, ADC/DAC |
| Real-Time Capability | Limited | High-precision multitasking |
| Safety | Basic watchdog | ISO 26262 ASIL-D, cryptography |
| Power Management | Minimal | Dynamic voltage scaling |
| Scalability | Constrained | Future-ready architecture |
Outcomes
- Zero functional deviation from SH2A behaviour
- Improved real-time performance with multi-core processing.
- Verified ASIL-D safety compliance.
- Lower power usage through dynamic scaling
- Future-ready ECU architecture
- Migration method reused across ECU portfolio.
Technologies Used
- Microcontrollers: SH2A, RH850
- Compilers: HEW, GHS
- Peripherals: Ethernet, CAN, ADC/DAC
- Testing Framework: Automated equivalence testing
- Safety: ISO 26262 ( ASIL-D)
- Power Management: Dynamic voltage scaling
