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I'm using modbus to interface my VFD to UCCNC. On the UCCNC spindle setup tab, there are radio check boxes for PWM and Step/Dir control methods. Since one of the boxes must be checked, I chose PWM and left the pin/ports fields at 0's. I'm curious if any UCCNC or motion controller resources are being used for these spindle control methods when modbus is used instead. Should there be a modbus radio check box added to disable any unnecessary PWM or step/dir stuff?

Frank

There are only 2 hardware modes for spindle configuration, the PWM and the Step/dir spindle modes.
And it then does not matter if you configure the spindle to PWM or Step/dir mode if you will not use those signals.
If you will control the spindle via modbus registers then you will first setup a modbus connection and at least one modbus function which will send modbus register values to the spindle.
And then you also will write some macros and macro loops to change your modbus register values which values will be send to the VFD via the modbus connection and modbus function.
The software does not know how your software communicates with the spindle, but you have free hands to code these macros based on what register values your VFD will need to receive for the different commands.

Finally I again want to mentioned that I don't think that full control of the spindle via modbus is safe, I think it is a much safer way to control the spindle speed via modbus,
but keep at least the spindle start/stop/enable signal to be controlled by the physical spindle relay output interruptable also with an external e-stop button.