A programmable controller sequentially executes a control program at a basic "scan rate" determined by the length of the program and the speed at which the controller processor executes the instructions therein. At the completion of each scan through the control program an I/O scan is performed which inputs the status of all sensing devices to the controller image table and outputs status data from the image table to operating devices. The present invention enables the status of selected sensing devices to be inputted and acted upon at any point during the scan through the control program and it enables the output of the processor logic unit to be coupled to a selected operating device at any point. The rate at which selected I/O devices can be scanned by the controller is thus programmable and may be much higher than the basic scan rate of the controller.