Does the 6509 need pullups to emulate a DIO-96?

[LV_Pro]

Hi all,

   We managed to damage a DIO-96 card in one of our new test stations, and in trying to get it up and running I swapped in a PCI6509 from another computer. It mostly worked, but we were seeing unconnected inputs getting false and random data. The board is in the tri-state configuration, and when I looked at the specs for the DIO-96 I noticed that it has 100K pullups, so we tried that on the unconnected inputs, which seems to fix the problems. Should we have to add external pullups, or is there something that my tired brain isn't thinking of? Most of the NI site shows the 6509 as the prefered replacement for the DIO-96, but nowhere did I see an* with a

*requires external pullups

Thanx, as usual

P.M.

[Laura F.]

Hello Putnam,

It is true that if you read a tristate (high impedance) line you cannot know for sure if you will read a 0 or 1 since you are not driving that line.  If you want the same behavior as the DIO-96, you do need to add the external pull-ups.  However, note that you can set the power-up state of your unconnected lines on the 6509, which you can't do with the DIO-96.

Thanks,

Laura