Distributed drum emulating programmable controller system

Abstract

Master units and slave units are preferably housed in identical housings. Each master unit comprises a Central Intelligence Unit (CIU) which in turn comprises a drum processor and a communications processor, and an Input/Output Unit (IOU) having input terminals and relays for connection to external devices. Each slave unit comprises an IOU. Each IOU is connected to its CIU through a Local bus (L-bus). Up to sixteen IOU's may be controlled by a single CIU. Up to 16 master units may be connected together by means of console bus (C-bus) and a data exchange bus (X-bus), in which case each master unit is given control of specified 'X' variables for update. Each 'X' variable has a specific time slot on the X-bus and all 'X' variables are stored on an X-drum at each master unit. The C-bus may be connected to a computer terminal at each master for programming of all CIU's, or to computer devices, or to long distance communication lines. Each IOU monitors continuously 32 identical input ports and maintains in a table the voltage at that port, whether the voltage has gone up or down through preselected voltages and the number of times this has happened since the last interrogation by its CIU on the L-bus. These tables are transmitted upon interrogation to its CIU. The program at the master can therefore interpret each input as a voltage, a switch, or a pulse source. Each IOU employs a digital filter in its program for interpreting the voltage of the inputs.