This seems similar to how I have heard embedded hardware operates with simple loops.

I might not be getting the controller correctly here, but I just want to check what exactly does the datapath refers to? In the slide, it mentions that the inner controller is a datapath consisting of only primitives nodes such as arithmetic, if-then/mux, memory-access. These seem to be primitive execution, and is the node basically the data path?

I'm little confused here as well. I think datapath refers to a chain of logic blocks that can be taken as a unit, i.e. implements a single operation. It eventually gets implemented as a circuit, so you put data in at one end and get data out on the other end, which may imply memory access. It may be the case that inner controllers aren't supposed to hold certain internal state, though of course they can access memory and change the state of the system as a whole.

@wkorbe Are you referring to the internal workings of one small embedded device? Or are you talking about multiple devices where each device might function as a controller?

@kkim801 The way it has been described to me, a piece of embedded software running on simple hardware just executes a loop, takes input, does some operations/computations, and produces output, then waits on input again, looping forever like this. There isn't an OS or threads. Spatial seems to allow defining similar loops.