WCRT Schedulability Analysis for CAN Bus Frame Priority Assignment
Mathematical derivation of Worst-Case Response Time (WCRT) calculations, preventing bus starvation and guaranteeing hard real-time deadlines for safety frames.
CAN bus arbitration relies on carrier-sense multiple access with collision resolution (CSMA/CR) based on frame identifier priority. If lower-priority safety-critical messages (e.g., steering torque feedback) share the bus with high-frequency telemetry, unmanaged frame collisions can cause deadline misses.
WCRT schedulability analysis models the maximum latency (R_i) of frame i: R_i = C_i + B_i + I_i where C_i is the frame transmission time, B_i is the blocking time from an ongoing lower-priority frame, and I_i is the interference from higher-priority frames preempting frame i during its queuing window.
CAN Router tools calculate WCRT matrices across full bus loads (up to 80% saturation), automatically synthesizing optimal 11-bit and 29-bit identifier allocations to guarantee zero deadline misses.