Rules for handling Don’t Care conditions in simplification process:
Prepare the respective map depending upon the number of variables used in the function.
Put 1 on appropriate places for every min-term provided in the function.
Put a CROSS ( X ) on every min-term showing Don’t Care condition.
Make pairs of 1’s in the map. Consider the CROSSes also like a 1 in the map, since we Don’t know
whether that min-term is a 0 or a 1.
If any Don’t Care min-term is left unpaired, leave it. No any evaluation is required for this unpaired minterm,
as it is a Don’t Care condition.
At last, deduce the expression simply like a normal K-map.
Don’t Care condition is a significant issue in understanding and simplifying Boolean expressions. Since its
name is pretty much descriptive, a Don’t Care condition simply means that the machine is not sure about
its output. On the same min-term, it can be 0 or 1.
These conditions are marked as a cross ( X ) in the K-map, and are evaluated simply as other min-terms.
Don’t Care terms are feasible for evaluation but only as far as they contribute in making larger groups
thereby improving the simplification.
Ex.Simplify the following function in SOP form using K-map method.