On 02/27/2011 04:22 PM, Peter Blodow wrote:
>
>> Peter,
>>
>> I work on a daily basis with Ethernet as a system and network
>> administrator.
>>
>> We're talking about a Real Time Ethernet, with a dedicated master and
>> slave network interface, which should preclude any worry of collisions
>> on a duplex connection between the two. Modern systems with full duplex
>> connections no longer really rely on CSMA/CD. As defined in 802.3,
>> that's just one of the protocols that have been used, not the only way.
>>
>> The reason we're talking about Ethernet as one of the possibilities for
>> communications between the computer and the controller is the
>> possibility of the ultimate demise of the parallel port, and the
>> difficulties of real time communications on the USB bus.
>>
>> So, Real Time Ethernet ain't quite your Granddaddy's TCP/IP or USB
>> protocol.
> Well, Mark, my granddaddy died in 1960. Concerning Ethernet, I was
> thinking of the times when I worked close to the IEEE 802 group way back
> when Siemens participated in technical innovation...
>
> It's just that I was so happy that PC's, being cheaply available and
> relatively easy to write programs for, have such a simple port as the
> parallel is. Well, I either will have to get used to the idea of writing
> special programs for dedicated processors again or else....??
>
> Whenever I had the impression to have cought up on technological
> development, it was running away again...
>
>
> Peter Blodow
Peter,
The "Granddaddy's TCP/IP" was just a figure of speech. We use it a
bunch over here when we talk about "new and improved" things. It was
first coined in the US auto industry. I hope I haven't given you the
impression I dislike the use of the parallel port for what we are doing
with it, far from it. This is just a look ahead, to get some ideas for
when the parallel port is no longer supported in the industry.
It would be nice if there were some other port available that would
work in real time, and deliver the throughput and versatility we need as
good or better than the parallel port.
Problem with PC's you buy off the shelf, they really aren't designed
with industrial use or motion control in mind. They're for Sally to
read her email, and play around on Facebook, or the gamers, or the
Word/Excel/Powerpoint crowd. We make the best with what we have, but we
also need to look to the future when certain features we've become used
to having around are no longer there.
I've got a bunch of old parallel port cables laying around with
Centronix connectors at one end. Who knew they'd stop supplying
interfaces that matched up with those cable ends?
Mark
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