DATA COMMUNICATION SYSTEM

A serial data communication loop system has a stored program computer capable of performing the sequences of internally stored instructions and also modifying those instructions as directed by those instructions. A loop controller includes the computer and generates timed spaced multiple bit message frames for serial, time spaced communication with a plurality of remote stations, each of which has one or more functional point modules. The multiple bits of frames are functionally grouped to provide in sequence a remote address byte, a module address byte, a command and status byte and a data and load selection byte. Each frame bit is immediately processed and transmitted to the next remote, either modified or unmodified in accordance with the system response without local synchronization generators or the like for simultaneously processing the several remotes. Each remote has a frame generator responsive to failure to receive a message frame within a given time to generate frames with its own address to signal the controller of a loop break. An operator console has a manual input means and output display means for selective communication with the other remotes under control of the loop controller. The display means includes individual status lamps for each remote as well as common display means selectively related to any one of the remotes. A plurality of loop system controllers connected to a central processing unit provide expanded capabilities.