Programmable controller processor module having multiple program instruction execution sections

In a programmable controller having input and output modules that interface electrical signals with sensing and actuating devices on machinery operated by the programmable controller, the input and output modules being connected to backplane buses;

• a processor module comprising:
• a first memory means for storing data representing status of the sensing and actuating devices;
• a second memory means for storing a control program defined by the user, which control program uses the data stored in said first memory means and which control program is written in a programming language consisting of a set of control program instructions;
• a logic circuit means for executing a first subset of control program instructions;
• a custom microcoded processor means for executing a second subset of control program instructions, which second subset is non-intersecting with the first subset;
• a general purpose processor section including a microprocessor to execute a third subset of control program instructions which third subset is non-intersecting with the first and second subsets, a read only memory for storing a program which the microprocessor executes, and a group of address, data and control buses to which the microprocessor and the read only memory are connected;
• a control program instruction decoder which responds to control program instructions read from said second memory means by enabling either said logic circuit, said custom microcoded processor or said general purpose processor section depending upon which one is able to execute each such instruction;
• an interface circuit, coupled to the backplane buses, for controlling the exchange of data between said first memory means and the input and output modules;
• and
• a set of buses to which said memory means, said interface circuit, said logic circuit means, said custom microcoded processor means, said general purpose processor section, and said control program instruction decoder are connected to exchange signals.