Why does my NIDAQ application behave correctly on a P233 WinNT 4.0sp6 system and incorrectly on a P3-600 Win NT 4.0sp6?

[Calimetrics]

I have two WinNT 4.0sp6 systems. One is an old Gateway P-233 and the new one is a P3-600 industrial rack mount system. The PCI-6503 behaves properly on the old system but it badly misbehaves on the new, fast machine. Specifically, we send a 16-bit value that the hardware uses to apply a DAC voltage to a motor. The motor works right on the older system but the motor is out of control on the new. Any ideas?

[Ben]

I would like more info.

If you scope the signals output by the 6503, are they doing what they are supposed to do?

Are you gettings any errors when writing to the 6503? If so, what are they?

Ben

[Michael_S.]

Hello,

Here is my best idea to the issue:

The PCI-6503 uses software timed Digtial I/O, so you probably call DIO Write several times in your program and the timing between when each DIO is executed is software timed. Your program probably runs slower on the P-233 and your DAC/motor can keep up with the rate of change on the 16-bit value being sent. Your P3-600 probably runs your program alot faster and the DAC/Motor may not be able to keep up with the rate of change of the 16-bit value.

You may consider adding a delay in your program between each update of the 16-bit values.

[Calimetrics]

Thanks to the two enthusiasts who provided some guidance. The application works properly when doing simple things but complex manuevers are a problem. So the software-timed I/O is probably the place to go. I haven't had the time to scope out the signals but that is the next step. Thanks again!