PROGRAMMABLE CONTROLLER WHICH ALLOWS FOR REMOVAL OF THE I/O MODULES DURING AN ON-LINE MODE

摘要

A programmable controller that allows input and output modules to be changed during an on-line mode with minimal interaction by the user. The controller includes a request table that separately stores change request signals generated by each module. In a first embodiment, the controller periodically polls this request table to determine whether any module has issued a change request. The controller disables each module that issues a change request. When a new module is loaded, the controller enables this module once the corresponding change request signal is removed from the request table. In a second embodiment, the controller uses an interrupt circuit to interrupt processing when a change request is initiated.