24 V I/O PC Card with hardware interrupt capability


Thread Starter

Joe Lill

I need a PC I/O card that has an ActiveX or standard dll interface that will provide a change on I/O event. The I/O card will receive 8 inputs and generate an event if the state of any of the I/O points change. Pulling data requires to much of the CPU, so I would like the board to generate a software event. I have talked to a couple manufacturers of data aquisition equipement and none of them gave me a sensable solution.

Curt Wuollet

That's because it's fairly difficult to do in a general way entirely in hardware. you would need dual registers and an n-bit comparator or something close and some sort of update logic so that the comparison register would update to the new data after the interrupt was handled so it could recognize the next change. These days it would probably be easiest to use a microprocessor and handle the logic in software.

I suspect there isn't enough demand for this sort of thing as any reasonably efficient software can achieve the same effect without hardware support or consuming excessive resources. We're only talking about one byte of data. Something is pretty bogus somewhere if you can't read or write one byte of data at extremely high rates, at least in automation terms, on a machine capable of several hundred MIPS.

Perhaps if you decouple your display rate from your scan rate?