Position vs Velocity mode

Page 6-39 of the ASDL-A3 drive manual shows support for an Inc. scale interface input for CL mode internal to the drive on CN5 pins 1-9.

I have doing some experiments today and it is possible to run ethercat sync below 1ms interuption.. I have tried 250us sync and it was fine... but I do not know how it will be outside of bench top ...my prehistoric servo drivers has limit at 250us ... I did not test them with sync motion just communication setup and I have generic ec driver only... 

It should be great to test them then anyway.. 

I followed with interest the initial discussion on the machining precision, with respect to the response delay of the motor position, via PDO to the LNCNC. In reality the numerical controls, for example Siemens 840d, have 2 parameters for each axis, which are the coarse stop and the 'precise stop. The problem arises, for example, when you finish one movement and start the next. Siemens at least waits for the axis interested in making the first movement to return to the precise stop control window.
Only after returning to the precise positioning window will the next line be executed.
LNCNC does not have this parameter, so in reality the passage between one movement and another does not take into account the real position of the axis, unless it is in the following error window.
Therefore, a tracking error that is too high, or an excessive delay in the information via ethercat, will lead to a premature transition to the next line of gcode and therefore a profile that is not perfectly equal to the programmed one, especially when you go faster.

Hi!
@zmrdko : 
thank to you and other experienced users in this thread for educating other folks and providing invaluable linuxcnc knowledge. I have some follow up questions on one of your posts:

- Would you mind sharing which z390 motherboard manufacturer / series do you have that allowed you to achieve 2.3us latency?
- What Intel PCIe Ethernet card did you choose? I saw that in this thread: gitlab.com/etherlab.org/ethercat/-/issues/104 they recommended "cheap realtek 100mb/s" ethernet card.
- Did you go with intel integrated graphics?
- IIRC, you (or maybe other user?) mentioned that with newer kernel the performance dropped from 8kHz (at 4.19rt) to 4kHz.
- Were there any other factors that positively affected performance besides the servo thread latency to get 8kHz? (e.g. ethernet roundtrip was quick)
- Have you measured how long does it take to execute your HAL components in each control cycle?
- Is there some other computer hardware that you leaned about and would be eager to try out with EtherCAT?

I hope this is not too much off-topic. Please correct me if there is a better form to ask these questions.

Thank you for your consideration,
Regards, Jakub