Eliminating Priority Inversion and Latency Jitter in Multi-Drop Automotive CAN Networks

Abstract: Mitigating transmit queue priority inversion and bit-stuffing induced latency variations in high-density automotive controller networks.

1. Priority Inversion in Microcontroller Mailboxes When multiple internal software tasks write to limited hardware transmission mailboxes, an internal priority inversion can occur: a low-priority frame occupying a hardware buffer can prevent a newly arrived high-priority frame from arbitrating on the bus. This paper presents an abort-and-reorder hardware queuing algorithm that guarantees immediate preemption.

2. Bit-Stuffing Latency Modeling Classical CAN inserts an opposite-polarity stuffing bit after 5 consecutive identical bits. In worst-case scenarios, a 64-bit frame payload can expand by up to 24 additional bits, introducing non-deterministic transmission jitter. Under CAN-FD, fixed stuff-bit counters and parity protection minimize this variation, enabling deterministic time-triggered scheduling.