Figure 8. NULL Convention half-adder circuit behavior.

Another important point to make is that if the mutually exclusive assertion convention is enforced for the input of the circuit, then the circuit itself maintains the convention at its output . A system of such circuits communicating among themselves will maintain the convention among themselves. The convention only has to be explicitly enforced at the input to the system. It is self maintaining within the system.

The NULL Wave Front Again

A single data value NULL Convention Logic circuit still has to be returned to an all NULL state before accepting a new input data set to resolve. As can be seen from the above examples, when a gate falls below its threshold it will assert a NULL value. The result values can become all NULL while there are still DATA values lingering on the input and internal to the circuit as shown in Figure 9.

Figure 9. Lack of completeness of input criteria for NULL.

This is identical to the situation with the previous Boolean logic examples and the same two solutions apply. There is a feedback solution and an Intermediate value solution.