So whiteout writing a white paper on Computer science I'll just copy some data from an online article:Dave_C,
you are still preaching the "faith" reason for not using an USB-Ethernet adapter but you haven't given one good fact other than "Centroid said". The fact that Windows could interrupt CNC operations with messages is a general Windows issue and not Ethernet Adapter specific.
-swissi
USB is a serial bus.
It uses 4 shielded wires: two for power (+5v & GND) and two for differential data signals (labelled as D+ and D- in pinout).
In a USB data cable Data+ and Data- signals are transmitted on a twisted pair with no termination needed. Half-duplex differential signaling is used to reduce the effects of electromagnetic noise on longer lines. D+ and D- operate together; they are not separate simplex connections.
USB supports four data rates:
Low Speed (1.5 Mbit per second) that is mostly used for Human Input Devices (HID) such as keyboards, mice, joysticks and often the buttons on higher speed devices such as printers or scanners;
Full Speed (12 Mbit per second) which is widely supported by USB hubs.
Hi-Speed (480 Mbit per second) was added in USB 2.0 specification. Not all USB 2.0 devices are Hi-Speed.
SuperSpeed (USB 3.0) rate of 4800 Mbit/s (~572 MB/s).
A USB device must indicate its speed by pulling either the D+ or D- line high to 3.3 volts. These pull up resistors at the device end will also be used by the host or hub to detect the presence of a device connected to its port. Without a pull up resistor, USB assumes there is nothing connected to the bus.
My input from here:
USB is a BUS and as such it has to share its workload with all other USB attached peripherals such as Keyboards, Mouse, Printer and all other such USB items.
USB is not full duplex!
USB only has a 2 wire transmit receive setup, while Ethernet is full duplex.
USB takes 20% of the available speed for housekeeping (overhead)
The real details are easily found by doing simple Internet searches so if you want to learn more, just google your questions until you are satisfied that Ethernet and USB are not the same!
Dave C.