Async FIFO CDC · cdc-rdc

Part 3 · CDC Protocols and Handshakes · All levels

4topics
4lessons

An async FIFO is the standard answer for streams across unrelated clocks, and it is also the structure signoff scrutinises most closely: two pointers cross in opposite directions, the flags derive from stale information, and reset must agree on both sides. For the design-side construction see the async FIFO RTL lessons; this topic teaches what a reviewer, the structural checks and the verification plan demand from it.

Lesson	After it you can...
Gray Pointers in Signoff	Say what makes the pointer crossing safe and what a check looks for.
Full and Empty	Explain why conservative flags are safe in both directions.
Depth Sizing	Size depth from burst length, rates and synchroniser latency.
FIFO Reset and Tool Checks	Reset both sides correctly and read the tool expectations.

Suggested order: read the four lessons in page order, then continue to CDC Protocol Verification.

Check yourself Why does signoff care about an async FIFO more than about a single-bit synchroniser?

A FIFO has two crossings in opposite directions, flags computed from stale pointers, and shared reset state: each of those is a separate way to corrupt data silently, so each needs its own check.

Up nextGray Pointers in Signoff

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