A multi-bit value whose bits can change together must never cross on bare per-bit synchronisers: the destination mixes old and new bits. Each strategy below replaces hope with a mechanism — hold the data still and say exactly when to look. Pick by rate, latency budget, and whether the far side must acknowledge.
Lesson | After it you can... |
|---|---|
Cross occasional words with a load pulse and state the timing rules. | |
Move control words with request and acknowledge and cost the latency. | |
Say what a shared RAM solves, what it does not, and where it hazards. | |
Capture quasi-static buses and list the proof obligations. |
Study in order: recirculation first as the simplest held-data scheme, then handshake, then RAM, then the quasi-static special case. Streams and bursts belong in a FIFO instead (see async FIFO design).
Qualified capture or mux recirculation: the value is quasi-static, so holding it around a qualifier is cheap and exact. A FIFO moves streams and would add memory and pointer logic for nothing.