uC port               CI or whatever out
P0.0 P0.1 P0.2 ... - CS0 CS1 CS2 CS3 CS4 CS5 CS6 CS7 ...
   0    0    0         0   0   0   0   0   0   0   0
   1    0    0         1   0   0   0   0   0   0   0
   0    1    0         0   1   0   0   0   0   0   0
   1    1    0         0   0   1   0   0   0   0   0
   0    0    1         0   0   0   1   0   0   0   0
   1    0    1         0   0   0   0   1   0   0   0
    .........       ...........................