isoSPI in a common ground system

Yes, isoSPI will work even if both ends of the link share a common ground.  You don't need to configure it any differently than if it were on a link that did need isolation.

That being said if you have a common ground the only benefit to isoSPI over SPI is longer cable length and improved EMC performance.  With a common ground and short bus length you're often better off just using standard 4 wire SPI.

Thanks for your reply.

We have a shortage of space. Can I connect the master and slave directly without an insolation barrier and only use a CMF?

If the insulation barrier is required, can I use a capacitor and maintain the full functionality under the EMI test (in this case, the pull-up resistors cannot be higher than 100Kohm as our system is low power)?

The signal barrier is less than 1m, and the EMI criteria is 3v/m performance.

Thanks in advance for your reply.