In IRC interrupt routine I sometimes get values of IRC_A_MON and IRC_B_MON which are the same as in the interrupt that follows. So the status changes of IRC_{A,B}_MON are like this: [...] 0 2 2 3 3 1 1 0 2 2 3 3 1 1 0 0 2 2 3 3 1 1 0 0 2 3 1 1 0 0 2 2 [...] However, absolute position computed from such status changes seems to be correct. Spin in one direction for a given time then spin in the opposite direction at the same speed for the same time returns to roughly initial value. The difference from initial value is only about tens (one step in absolute position corresponds to one interrupt). Besides, in some cases (tens of hundred thousands interrupts) I read zero from IRC_IRQ_MON, but interrupt source is setup to rising edge, so I'd expect '1' every time. Have anyone encountered similar issue or do you have any explanation for this behavior? Thanks Jaroslav Beran