= "2" |- | m10 || || m(10,11) || || m(10,11,14,15) || |- | || || m(10,14) || ||colspan = "2" |- | m12 || || m(12,14) || ||colspan = "2" |- | rowspan="2" | 3 | m11 || || m(11,15) || ||colspan = "2" |- | m14 || || m(14,15) || ||colspan = "2" |- | rowspan="1" | 4 | m15 || || | | colspan = "2" |} Note: In this example, none of the terms in the size 4 implicants table can be combined any further. In general this process should be continued (sizes 8, 16 etc.) until no more terms can be combined. Step 2: prime implicant chart None of the terms can be combined any further than this, so at this point we construct an essential prime implicant table. Along the side goes the prime implicants that have just been generated (these are the ones that have been marked with a "" in the previous step), and along the top go the minterms specified earlier. The don't care terms are not placed on top—they are omitted from this section because they are not necessary inputs. {| class="wikitable" style="text-align:center;" |- ! || 4 || 8 || 10 || 11 || 12 || 15 || ⇒ || A || B || C || D |- | style="text-align:left;" | m(4,12) || || || || || || || ⇒ || || 1 || 0 || 0 |- | style="text-align:left;" | m(8,9,10,11) || || || || || || || ⇒ || 1 || 0 || || |- | style="text-align:left;" | m(8,10,12,14) || || || || || || || ⇒ || 1 || || || 0 |- | style="text-align:left;" | m(10,11,14,15) || || || || || || || ⇒ || 1 || || 1 || |} To find the essential prime implicants, we look for columns with only one "✓". If a column has only one "✓", this means that the minterm can only be covered by one prime implicant. This prime implicant is essential. For example: in the first column, with minterm 4, there is only one "✓". This means that m(4,12) is essential. Minterm 15 also has only one "✓", so m(10,11,14,15) is also essential. Now all columns with one "✓" are covered. The second prime implicant can be 'covered' by the third and fourth, and the third prime implicant can be 'covered' by the second and first, and