Figure 8. NULL Convention half-adder circuit
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
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