Observations on Single Data Value NULL Convention
A single data value NULL Convention Logic circuit
can be conveniently monitored for faults in such
a way that it cannot tell a lie as shown in Figure
Figure 17. Fault monitoring NULL Convention
If exactly one DATA value is asserted in each
output group it is the correct resolution of a
complete input data set. If there are ever three
DATA result values simultaneously asserted, it
is an error and the threshold three gate will
announce the error. If the circuit only asserts
one DATA result value it will fail to announce
completion of resolution and this can be detected
with a watchdog timer. A NULL Convention Logic
circuit will always either:
1. Assert a correct result.
2. Fail to complete resolution.
3. Assert an explicit error signal.
A fault will be detected as soon as it causes
an actual resolution error. This holds for all
single point faults. It is possible for a NULL
Convention Logic circuit to tell a lie but it
requires two coordinated faults that produce a
valid encoding which is, nevertheless, erroneous.
Single data value NULL Convention Logic circuits
are similar to neural nets as shown in Figure
Figure 18. Similarity to neural nets.
The single data value NULL Convention Logic circuit
in the middle performs the same discrete symbolic
processing as the Boolean circuit at the top,
while at the same time being a more complete and
autonomous expression of the process than the
Boolean logic circuit. The fully connected neural
net at the bottom, with an input layer, a hidden
layer and an output layer can be configured to
identically match the NULL Convention Logic circuit
by setting the thresholds of each node and setting
the weights of each connection appropriately to
zero or one. The NULL Convention Logic circuit
might be viewed as a pretrained neural net.