Why is my digital line set to high when closing LabView?

[Maxime]

First of all, I just upgraded from NI-DAQ 7.1 to NI-DAQ 7.2. The following problem appeared just after this upgrade, without any change to the VI's.

I am runnning VI's that can control the state of a relay (connected/disconnected) using a digital line. For some reason, whenever I close Labview (not just the VI), that digital line is set to high, causing the relay to do an unwanted connection. Normally, the digital line should stay to the state it was when leaving LavView (it worked correctly before the upgrade of NI-DAQ).

For your information, I am running Labview 6.1 under Windows XP and my data acquisition device is a PCI-6110.

Any idea on how to solve this? Thanks in advance.

[JB]

See page C-6 What are the power-on states of the PFI and DIO lines on the I/O
connector? in the user manual of the PCI-6110.

It seems that the PCI-6110 enters in the reset state when closing LV. If you want a DO to be low in the power on and reset states, then connect a pull down resistor (3K9 or less).

Internal pull up = 50K, external pull down = 3K9 --> Uout_Low = 0.36V --> compatible with TTL.

[Maxime]

So you think that it has now become impossible for a DO to retain its state after leaving LabView? It now has to be either always low or always high?

[JB]

The same problem will appear on power on.

You must take care of this when designing the electronic.

[Maxime]

Ok, that's what I'll do;

Thanks for your help!

[Maxime]

I used a pull down resistor of 2.7k to get a low default state and it worked correctly.

Thanks again!

[JB]

You're welcome.