An interface for an industrial controller is provided that enables connection of different types of plug-in I/O modules to the industrial controller. The interface includes several mechanisms, which can be implemented through control logic, circuitry, and/or software, that enable the control/monitoring device to operate in conjunction with different types of plug-in I/O modules. According to certain embodiments, the interface includes setup mechanisms that enable initial communications between the plug-in I/O modules and the control/monitoring device. The interface also may include operational mechanisms that facilitate communication between the plug-in I/O modules and the control/monitoring device during operation. The interface further may include registers that store data for the plug-in I/O modules.