Hey guys,

I know how to find essential prime implicant terms when don't cares are not involved, but things get a little hairywhen they do. From my understanding, when we choose EPIs, we start from the lowest index minterm, ignore don't care terms and check if all of its adjacent minterms can be covered by a single group. If yes, check if the don't care can make this group larger, change its value to one and label it as an EPI. If not, Keep the don't care term's value zero and label the smaller group as EPI. Otherwise, just move to the next lowest value minterm

In this example, I don't get it why the group formed from cell 0 is not EPI, while groups formed from cells 14 and 7 are.

 

Recall that an essential prime implicant is a prime implicant that covers at least one case that cannot be covered by any combination of other prime implicants.

The cell 0 can be covered by two prime implicants, namely A'C' amd A'D'. Cells 7, 11, and 14 can ONLY be covered by the prime implicants shown.

 

n essential prime implicant is a prime implicant that covers at least one case that cannot be covered by any combination of other prime implicants.

Oh I see, thanks a lot.