>If I use int on change and both encoders change
>will I continualy miss one int to service the other ?
>Will this cause me to interpret the distance travled incorrectly ?

Using the "interrupt on change" feature has some specific gotcha's about it,
but depending on what you do with the other half of port B you may get away
with it.

If you have more than one encoder change state at the same time then
detection of both is a function of how you go about deciding which one
changed.

Hint - note that the interrupt on change only tells you that one of four
pins changed state, but not which one. Once you detect one change, it may
not be the only one.

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