Programmable controller with multiple task processors

The programmable controller for operating a machine to carry out a plurality of programmed functions, which comprises:

• a backplane bus having leads for conducting data signals, address signals and control signals;
• a plurality of processor means connected to said backplane bus, each processor means having a memory for storing user control programs for execution on that processor means and program execution sequence data comprising a plurality of descriptors each identifying a user control program, a transition condition which indicates when the execution of the user control program should terminate, and the next user control program to be executed and which processor means is to execute the next user control program, each of said processor means having means to transmit program execution commands to other processor means;
• an I/O interface means coupled to said backplane bus for coupling I/O devices to the programmable controller;
• and
• means for controlling access to said backplane bus by said plurality of processor means and said I/O interface means.