It's good to see that a recent update to the NI-845x API allows the NI-8452 to behave as a slave device.
We plan on using these for this purpose.
However, looking at the NI-845x Hardware and Software Manual (August 2012, 371746D-01) it is not apparent whether or not the NI-8452 can be configured to emulate more than 1 slave device at a time.
We need to emulate 2 slave devices on the same bus, can the NI-8452 API do this?
Unfortunately it does not support that feature, and probably won't do in the foreseeable future. You would to use multiple 8452 devices.