Peter Fitzsimmons wrote in a message to Gary Chambers:

Hey Pete!

 PF> You CAN do "in" and "out" from a user program
(ring 2/3), 
 PF> but not anything else (DMA, IRQs).   Also,  a user program
 PF> doing in/out do a very busy device (high throughput) is not
 PF> a good idea.

Actually, I don't *THINK* I'll be doing any more than READING from the
device. If I do any writing, I suppose it would be to "kick" the
device to give a current reading.  I can't imagine "high
throughput," either; perhaps reading the device anywhere from every 10
to 30 seconds (adjustable).

 PF> In the best situation,  you should write a device driver to
 PF> talk to the hardware,  but this is hard for the first timer,
 PF>  and I can understand why you might opt for the user program
 PF> solution.

This is really what I wanted to avoid, but if it turns into a full-fledged
weather station, complete with satellite reception ;-) I'll have to get the
device driver.

 PF> Note that the segments that do the in/out have to be marked
 PF> as "IOPL" in your linker *.def file.

Thanks for the very informative reply!

GeeCee/2 (Team OS/2) 
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