Yes, it is as simple as using two interrupts and forming a word from the interrupts. The length of the bits doesn't matter in the least - it can be as long as necessary. That's how all these 'custom' variations come about. After the timeout period (forgot what it's called right now), that marks the end of the word.

Thanks to DT_Ints, it's very simple, and checks out by comparing to a prox reader with a RS232 output. ;-)