Can you just tell me what sort of thing is supposed to happen when you detect a transition? Do you need to detect both ways? (high->low and low->high)?
For 8 of the pins (the EOC and EOA) I simply need to detect a lo to high transition. Usually the result is that one of the Gate pins (the only 4 outputs) is turned on or off. It is not as simple as looking things up in a table since there are conditional results based on the mode your are in for that channel and whether or not the gate output is already high.
This logic has been reduced to the basics in my non-isr version.
The trig inputs I use a detect change instead of just lo-hi since in some modes I need to know how long the pins are kept high (in this mode "AR mode" the gate output pin simply follows the trig pin. So while trig pin is hi, gate pin should be hi).
For processor I am using an Atmega168-20U (smd version).