NI_660x: can't use all encoders at the same time (ni 6602)

I am using a NI 6602 card, but I haven't been able to use all the 
counters at the same time.
When I configure and read counters from 0 to 3, they work correctly.
But if I also configure counter 4, they stop working. In this case, 
counter 0 and counter 4 give the same value, and counters 1-3 doesn't 
work. So it seems like counters 0 and 4 are using the same source.

I don't know why I can't configure to use them at the same time. I guess 
if counters 0-3 and 4-7 should be considered as in a different subdevice 
or something.
Anyone had problems when using all the counters at the same time?

Any help or idea would be very valuable.
Thanks in advance.

-- 
Lluís Duch
Unitat d'Assaig i Control

ENCOPIM S.L.
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