4 ms·
They mostly seem reasonable to me. I'm not sure exactly what they mean by external wire inputs in this statement: "Synchronize all external wire inputs with tw
by DigitalJack 9y ago
They mostly seem reasonable to me. I'm not sure exactly what they mean by external wire inputs in this statement: "Synchronize all external wire inputs with two clocks before using them."
You can ruin a design by trying to synchronize data. We've had to respin an ASIC because somebody "synchronized" the data on a bus.
- DigitalJack 9y agoAnd to clarify further, they mean two flip flops in series, not two clocks. It sort of becomes a short hand to refer to the delay incurred by flip flops in series as "clocks" (short for clock cycles). And to capture data in a flip flop is often referred to as "clocking" the data.
- blacksmythe 9y ago>> "Synchronize all external wire inputs with two clocks before using them." This is why you need to sync external (async) inputs: "Metastability in electronics is the ability of a digital electronics system to persist for an unbounded time in an unstable equilibrium or metastable state. In metastable states, the circuit may be unable to settle into a stable '0' or '1' logic level within the time required for proper circuit operation. As a result, the circuit can act in unpredictable ways, and may lead to a system failure..." https://en.wikipedia.org/wiki/Metastability_in_electronics
- mikeash 9y agoFormatting related aside: don't put spaces in front of your URLs, as that causes them to be formatted as code and makes them unclickable.