Different counting with different direction

[Jordi_Blanch]

Hi all.

I've an application where I use a LSI7084 to convert an encoder signals to a counter signals for a PCI6036E multifunction board. I've selected a resistance to have a 1 us pulse width on the 7084 output.

When I rotate the encoder in one direction it counts correctly 12500 pulses per revolution (the encoder resolution), but when I rotate the encoder on the other direction, the counter counts 25000 pulses per revolution (double of the encoder resolution).

But the most amazing point is that when I connect an oscilloscope to the counter inputs of the 6036, the counting seems to have magically fixed and I've 12500 pulses in both directions!!!

I'm completly lost and don't understand what's happening and why it doesn't work properly.

Could anyone give me a hand with this problem? Thanks in advance!!!!

[AnalogKid2DigitalMan]

Keep the scope permanently hooked up as part of the test system

My only guess is maybe you need a stronger pull up or pull down resistor for a cleaner signal, perhaps that is the function the scope is providing?

Do you have a good ground connection from the 7084 to the 6036?