A B C D | A | ( C & ~ D ) | ( B & D )
-------------------------------------------------------
0 0 0 0 | 0 0 0 0 1 0 0 0 0 0
0 0 0 1 | 0 0 0 0 0 1 0 0 0 1
0 0 1 0 | 0 1 1 1 1 0 1 0 0 0
0 0 1 1 | 0 0 1 0 0 1 0 0 0 1
0 1 0 0 | 0 0 0 0 1 0 0 1 0 0
0 1 0 1 | 0 0 0 0 0 1 1 1 1 1
0 1 1 0 | 0 1 1 1 1 0 1 1 0 0
0 1 1 1 | 0 0 1 0 0 1 1 1 1 1
1 0 0 0 | 1 1 0 0 1 0 1 0 0 0
1 0 0 1 | 1 1 0 0 0 1 1 0 0 1
1 0 1 0 | 1 1 1 1 1 0 1 0 0 0
1 0 1 1 | 1 1 1 0 0 1 1 0 0 1
1 1 0 0 | 1 1 0 0 1 0 1 1 0 0
1 1 0 1 | 1 1 0 0 0 1 1 1 1 1
1 1 1 0 | 1 1 1 1 1 0 1 1 0 0
1 1 1 1 | 1 1 1 0 0 1 1 1 1 1
A: momentary button
B: power turned off from other source
C: power turned on from other source
D: binary counter in 0 state