Digital output 9472 COM terminal- digital or analog ground?

Hello. 

I am using NI crio  9012, chassis 9103, NI 9472 Digital Output and NI 9225 Analog Input modules. 

Is the COM terminal of digital output module analog or digital ground? If it is a digital ground, should I connect the -ve of DC supply to 9472 directly to COM or should I place a capacitor or RC in between to separate analog and digital grounds?

I am connecting a 24V dc supply directly to the Vsup and COM of digital output module. Now the COM terminal of the digital oputput module will be analog ground or digital ground? 

Please help me soon. 

Thank You.