Layering

The framework is organized in three layers. Applications only ever call into Platform_RTE - never directly into the OS/RTOS - so retargeting to a different platform means registering a different OSAdapter (ADR-005), not rewriting application code.

OS Abstraction Layer (OAL) - one service per OS/RTOS primitive: Timer Service, Non-Volatile Memory, Static Memory Reservation, Task/Thread Scheduling, Inter-Process Communication, Point-to-Point Network Link, Logging and Diagnostics, Controlled Reboot. Every service validates parameters, then dispatches to an integrator-supplied OSAdapter (ADR-005); the framework itself ships no OS-specific code.
Common utilities - layer-agnostic building blocks with no OS dependency: Cross-Layer Data Buffer, Bounded String Manipulation, Checked Integer Casting, Common Types, Common Status and Error Codes, Safe-State Transitions and Checked Assertions.
Redundancy / vital communication - built on top of the first two layers: Channel Link (single redundant link) (one point-to-point redundant link), Voter (N-way channel voting) (N-way 2oo2/2oo3/NMR voting across registered Channel Link (single redundant link) instances), Cross-Comparator (2-way channel comparison) (2-way consistency check between two independent peer channels, ADR-025), Checkpoint Rendezvous (bounded checkpoint-ID rendezvous for cross-node agreement), Clock Synchronization (diagnostic/timeout-sizing only) (diagnostic-only wall-clock offset, never a correctness dependency), Checksum & CRC Utilities (CRC-64 data integrity), and Watchdog Mechanism (hang detection and recovery, including RTE_WATCHDOG_ACTION_FAILOVER for redundant-peer-loss reactions).

Application Manager sits above all three layers, giving an application a single init/execute/shutdown lifecycle entry point.

Common-Cause-Failure Mitigation

For SIL 3/4 dual-channel deployments, ADR-008 covers build-diversity mitigation (two independently-configured toolchains compiling channel A and channel B); Cross-Comparator (2-way channel comparison) (ADR-025) is the framework primitive that answers "do channel A's and channel B's results agree?" for exactly that kind of independent peer pair - it supersedes the ADR-008-era standalone comparator module, which was never built and has since been removed outright.

Where to Go Next

Getting started integrating an OSAdapter: App Manager Integration with Channels
Per-module architecture and user guides: see the "Related Pages" list (each module under include/rte/<module>/ ships an ARCHITECTURE.dox and USER_GUIDE.dox pair).
IPC transport choice: IPC Transport Selection Guide, Channel Configuration Guide
Channel topologies: Channel Topologies and Redundancy Patterns
Architecture Decision Records (design rationale, one per major decision): docs/architecture/ADR-*.md
Requirements traceability: Software Requirements Specification (SRS)
MISRA C:2012 conformance status: docs/MISRA_COMPLIANCE_REPORT.dox
Cross-compilation (Linux, QNX, etc.): docs/CROSS_COMPILATION.dox

+----------------------------------------------------------------------—+ | Generic Platform (RBC_GP) | | (ERTMS Procedures, Handover FSM, Route Management, 2oo2 Voter) | +----------------------------------------------------------------------—+ │ ▼ (rte_channel_open / rte_flow_write) +----------------------------------------------------------------------—+ | Safe Computing Platform (Platform_RTE) | +----------------------------------------------------------------------—+ │ ┌────────────────────────┼────────────────────────┐ ▼ ▼ ▼ +------------------—+ +------------------—+ +------------------—+ | safeApiProtocol- | | safeApiProtocol- | | safeApiProtocol- | | AdapterDDS | | AdapterSS098 | | AdapterEuroRadio | | (Trackside Bus) | | (RBC-RBC Fixed IP) | | (EVC-RBC Radio) | +------------------—+ +------------------—+ +------------------—+ │ │ │ │ └────────────┬───────────┘ │ ▼ │ +-----------------------------------—+ │ | safeCommFramework | │ | (SaF State Machine, 3DES MAC, KSMAC, | │ | CFM, ALE, Future RaSTA Engine) | │ +-----------------------------------—+ ▼ ▼ +----------------------------------------------------------------------—+ | OSAdapter (Platform_OS_POSIX) | | (Timers, Memory Pools, Raw OS Sockets) | +----------------------------------------------------------------------—+