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KNX ADVANCED COURSE

6.2.4 EXCLUSIVE OR Element (XOR)

If the output of the EQUIVALENCE element is negated by the series connection of a NOT
element, an element is created that always has the ‘1’ state at the output if the input states
are different.
This type of element is called EXCLUSIVE OR (= unequal value). The name suggests that
this element is an OR element in which case it is not possible to have a ‘1’ state at the
output if both inputs have a ‘1’ state (Case 4). The designation XOR was formed from the
English expression EXCLUSIVE OR. This term is also used in the German language.

A
= X 1 Z XOR
A B X Z
B
0 0 1 0
0 1 0 1
1 0 0 1
A 1 1 1 0
=1 Z

B

Figure 27: Origination of an EXCLUSIVE OR element with truth table and graphical symbol
(standardised)

The ‘1’ state is then always present at the output of an EXCLUSIVE OR element if the two
inputs have different states.
An algebraic equation for EXCLUSIVE OR can be taken in the following format from the
circuit in Diagram 6.10:

X = (A ^ B) v (A ^ B)
This expression is not fully negated since the NOT element is series-connected. The
following equation is produced for EXCLUSIVE OR:

Z = (A ^ B) v (A ^ B)

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