Re: dual processor for dual cnc machines

[Jon Elson <jmelson-at-artsci.wustl.edu>]

Spehro Pefhany wrote:

> At 02:48 AM 6/6/00 -0400, Jon wrote:
> >
> >The stepper systems need TWO parallel ports for ONE
> >machine.
>
> Is that because of the *speed* of the port or because more
> than so many axis were used?

The real reason is that the motion and limit switches functions are
handled by a program running in a real-time environment running
below the Linux kernel, and the auxilliary I/O functions are being
handled by a non-real time program running within the Linux
environment.  They could be made to co-exist with some difficulty,
but that hasn't been done.  So, they need separate ports.
Also, the number of available bits is limited, so it is not a severe
shortcoming.

Jon