Smart Transmitter Use as Controller

Fieldbus is a generic term. Foundation Fieldbus (FF) is a specific implementation of a Fieldbus.

The graphic for Foundation Fieldbus below shows loop control with only 2 devices, a sensor and a final control element, with the PID control functionality residing in the valve positioner:

And the graphic below expands to show the Function Blocks internal to the devices:

Graphics come from Samson's very well written tutorial on FF

http://www.samson.de/pdf_en/l454en.pdf

Profibus is definitely a Fieldbus, but it isn't clear to me whether field devices have contol capability in the Profibus architecture.

Not yet, because the <...we...> doesn't understand it.