A method and system for assigning slot addresses to modules in an industrial control system is disclosed. The modules are set up in a daisy chain topology. On power-up, a first module in the chain reads its slot address from a user configurable input or sets its slot address to a default value. The first module communicates to its immediate right neighbor using a special, one-hop message. The neighboring modules communicate to receive each other's information. The first module then sets an enable signal between the modules and sends a slot number to the neighbor in a firmware message. The neighbor checks if the enable signal is set and verifies that the slot number is a valid slot number. If so, then the neighboring module accepts the slot and repeats the same procedure to its next immediate neighbor, and so on until the last module.