Re: [CAD_CAM_EDM_DRO] Re: Black box ??

Larry Edington wrote:

> Parallel ports are going away. Except as add in PCI cards which of course
> will
> require drivers as it's not a legacy implimentation and can't be decoded in
> the
> standard legacy I/O space. A year from now I would think it will be very
> very difficult
> if not completely impossible to find an off the shelf PC or system board
> with a legacy parallel port on it.

I seriously doubt it. It will happen, but it will be much longer than you think
before they disappear form ALL computers. And, the PCI cards may not be
that hard to use, especially in my particular setup.

> It is possible to write a driver to
> intercept parallel port I/O calls and route it to a PCI based parallel port.
> But, that's not the most robust way to handle an I/O port. Not to mention
> the problems that can be introduced by other drivers trying to do I/O
> intercepts.
>
> There will be hundreds of thousands of older PC's with the existing parallel
> ports out there. But to run the latest / greatest / fastest, you will have
> to find a different interface.
>
> It won't be long until we'll be "legacy free".
>
> USB 2.0 will be a good option.

USB may not work at all for the servo-like interface that I have been
using in all of my designs. There is a limit to the handshaking rate of
1 KHz on USB, and that is by the bus's timing, not anyone else's.
It might work fine if you throw out all the overhead and just use the
bare hardware. USB requires a CPU on the outboard device, mine
doesn't. Hot swap causes a temporary lockup of the bus, so you can't
allow any hot swapping while the machine is running.

> 10 / 100 Ethernet will be a good option.

Ethernet is not time deterministic, but it should have enough bandwidth
for most home users. But, it still can't come anywhere near one machine
instruction for each byte transferred, in small handshake transfers of a
dozen bytes or so.

Jon