How do function blocks work in Foundation Fieldbus systems?

Foundation Fieldbus function blocks: standard building blocks for control applications defined by Fieldbus Foundation. Types: transducer blocks (interface to physical I/O), resource blocks (device information), and function blocks (AI, AO, DI, DO, PID, etc.). Execution: function blocks run in field devices or host systems on scheduled time, input connections receive data from other blocks, algorithm processes inputs, output connections transmit results. Control in field: PID block in valve positioner receives AI from transmitter, calculates output, and controls valve directly - reducing host controller load and improving response. Link Active Scheduler (LAS) manages execution timing for deterministic control.