How do I code the Mach3 plugin(dll)  with c # or delphi....?
Is there a source document?

Which Mach3 plugin are you referring to ?

Tweakie.

I programmed my own cnc control card.
I am trying to make my CNC control board compatible with mach3.
Therefore, I must encode the plugin.

In that case you would program in C / C++ and there is no source code, as such, available but blank plugins are available to get you started. There are also tutorials, here is one you can download; https://www.machsupport.com/forum/index.php?action=dlattach;topic=7922.0;attach=6167

Tweakie.

  Thanks

Reading g code from sd card .

Great job!