Hi Gene,
So once you've bought the controller, there is no other restriction. And
I assume that royalty is 2x per axis, once for each end of the cable.
No, they don't charge twice.
Part of marketing a Fieldbus-System is to make it widely accepted in the
industry, so Beckhoff
(and others like Siemens with Profinet) has/have to find a balance
between protection and easy/low cost accessibility.
From my understanding Beckhoff is very open regarding the master (who
even does not need a special hardware,
when driven by an RTOS) and are very restrictive when it comes to the
slave (where a ASIC / FPGA is needed in any case)
Makes also sense from commercial point of view, because in a typical
system there are much more slaves needed that masters.
Or can one receiver handle more than 1 axis with acceptable latency?
A slave in EtherCat's daisy chain topology has an input and an output
Interface. (the biggest difference to most other ethernet based fieldbusses)
The incoming stream is shifted out with 1 bit delay to the output.
At 100Mbit/s -> 10ns delay added up to each slave in the chain.
The difference between one slave 3axis servo pack and three single axis
servo amps is ~20ns.
But to synchronise the output, all slaves have to wait for the full
frame received.
Even on a 10 axis system this does not even come close to the total
frame time.
Not to mention the jitter caused by a (soft)RTOS
cheers
Rainer
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