I'll be using EMC, and would also like to try out Mach2 for my mill.

Using the parallel port for IO there is a shortage on inputs, so as far as I can see I must wire-or several switches to one input. What is the best way to do it.

My guess is to wire-or all +limits and -limits, then use separate home inputs.

My reasoning is that if one axis is sitting on its home switch, the program cannot sense that another axis is tripping it's home switch. I imagine this must be undesirable?

But the end limits are not supposed to be tripped during execution, and would need operator intervention anyway. Am I right?

I need inputs for Estop, A axis home (index), drive fault and ready (wire-ored) , ditto for VFD, probe and probably some I didn't figure in yet, so any common use with little compromise will be good. Do you have any experience to share?

Adding to the fun, I have 2 Z-axes: the knee and the spindle. That's another challenge, if I can let the controller handle both. It should, but I guess it does not know that they both affect the Z position, and handle that intelligently.

If EMC and Mach2 have different limitations, I can use a printer selector box to reshuffle the pins, but I would rather not unless needed.

ESjaavik

I haven't tried ot yet - but MACH2 will take (and use) 2 ports - you can set up another by adding a second card to the pc if you've got the slots. The configure lets you get to the second card for more "wire access".
Maybe with a USB version we'd have more options? HINT HINT - hope you're listening ART! hehehe
Hope that helps - Cheers - Jim

Also, both pieces of software can be configured to back off of a home switch when it hits it, until the switch opens. I have my homes wired in series, and as long as I home one axis at a time, it works great. But like High Seas said, if you can get a second parallel port (usually to be had on ebay for cheap, but not necessarily in your part of the world), then you have a big increase in inputs.
Actually, if you can't find one on ebay, I have one here that I can send to you for the cost of postage. It worked fine on Win2000, but when I upgraded the pc motherboard, this pci card stopped the pc from booting. Let me know.

Kong: Thanks, I appreciate it. But I'm in Norway, so the postage will probably be more than the $17,50 I have to pay for a new PCI printer card locally. What I'm worried about is it may not be as good for outputs as an old ISA board, but the inputs should work fine. I'll probably try that and see if that leaves me with separate home switch inputs. The outputs should also work fine if I make a buffer board, but I was hoping I could avoid it.

Since neither of you mentioned any problem with the limit switches wired in parallel (NO switches) or series (NC switches), I assume that works fine?