System for replacing control processor by operating processor in partially disabled mode for tracking control outputs and in write enabled mode for transferring control loops

In a distributed industrial process control system, a method for allocating process control, performed by a primary processor module, to a first processor module for purposes of thereafter providing control signal data, in accordance with multiple industrial process control loops executed by the first processor module, to industrial process equipment by means of a set of I/O devices communicatively coupled to an I/O bus, and wherein a bus arbitrator interposed between the I/O bus and the first processor module oversees write access by the first processor module to the I/O bus, said method for allocating process control to the first processor module comprising the steps of:

• installing the first processor module within the distributed industrial process control system, thereby establishing a communicative link between the first processor module and the I/O bus in order to sense transmissions from the set of I/O devices;
• first operating the first processor module in a partially disabled mode after the installing step, wherein write access by the first processor module to a data bus for controlling an I/O device in accordance with a process control loop is prevented;
• viewing a set of values provided by the first processor module while the first processor module is operating in the partially disabled mode in order to determine the proper operation of the first processor module;
• second operating the first processor module in a write enabled mode after the first operating step, wherein write access by the first processor module to the data bus for controlling an I/O device is enabled in order to transmit control signals, associated with ones of the multiple industrial process control loops for which write access is selectively designated, from the first processor module to the set of I/O devices;
• granting control authorization to the first processor module for a designated control loop of the multiple industrial process control loops;
• and
• selectively enabling write access by the first processor module to output a control value to be used to control an I/O device in accordance with the designated control loop.

In a distributed industrial process control system, an apparatus for allocating process control, performed by a primary processor module, to a first processor module for purposes of thereafter providing control signal data, in accordance with multiple industrial process control loops executed by the first processor module, to industrial process equipment by means of a set of I/O devices communicatively coupled to an I/O bus, said apparatus for allocating process control comprising:

• a bus arbitrator interposed between the I/O bus and the first processor module including security circuitry for limiting write access by the first processor module to the I/O bus;
• a mode selection switch for placing the first processor module into a set of operation modes including:
• a partially disabled mode wherein write access by the first processor module to a data bus for controlling an I/O device in accordance with a process control loop is prevented, and
• a write enabled mode wherein write access by the first upgrade processor module to the data bus for controlling an I/O device is enabled in order to transmit control signals, associated with ones of the multiple industrial process control loops for which write access is selectively designated, from the first processor module to the set of I/O devices;
• a supervisory control device for reviewing a set of values provided by the first processor module while the first processor module is operating in the partially disabled mode in order to determine the proper operation of the first processor module;
• means for granting control authorization to the first processor module for a designated control loop of the multiple industrial process control loops while the first processor module is in the write enabled mode;
• and
• means for selectively enabling write access by the first processor module to output a control value to be used to control an I/O device in accordance with the designated control loop while the first processor module is in the write enabled mode.