[PSR] IRC_SR register values in interrupts

[beranj25 at fel.cvut.cz]

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