FIFO — Data Integrity and Error Handling
Introduction
FIFO structures sit directly in the data path, making data integrity a primary design concern. This page focuses on architectural techniques for protecting FIFO contents, detecting corruption, and ensuring robust behavior under fault conditions.
Why Data Integrity Matters
A FIFO must guarantee:
- no data loss
- no duplication
- correct ordering
- reliable flag behavior
Faults such as pointer corruption, memory bit flips, or overflow/underflow can compromise system‑level correctness.
Pointer Protection
Pointers are vulnerable to:
- SEUs (single‑event upsets)
- CDC sampling errors
- wrap‑around misalignment
Protection techniques:
- parity bits
- ECC on pointers
- redundant pointer tracking
- pointer range checks
Memory Protection
FIFO memory may be implemented using registers, distributed RAM, or block RAM.
Protection options:
- parity per word
- ECC (SECDED)
- scrubbing for long‑lived FIFOs
Overflow and Underflow Detection
A FIFO must detect and report boundary violations.
Mechanisms:
- write‑when‑full detection
- read‑when‑empty detection
- sticky error flags
- optional error counters
Flag Robustness
Full/empty flags depend on pointer comparison.
Failure modes:
- incorrect flag due to pointer corruption
- metastability in synchronized pointers
Mitigations:
- redundant flag logic
- cross‑checking synchronized pointers
- registered flag outputs
Error Reporting and Recovery
Depending on system requirements, a FIFO may:
- assert error outputs
- trigger interrupts
- flush contents
- reset pointers safely
- enter a known safe state
Diagnostic Coverage
For safety‑critical systems, diagnostic coverage may include:
- detection of pointer corruption
- detection of memory corruption
- detection of overflow/underflow
- periodic self‑tests
