Methods and systems for secure control of system modes and sub-modes

A method of robustly representing data in a control system comprising a control module and a plurality of sub-modules using a data structure comprising a plurality of bits, wherein each of the bits is capable of representing at least a first value or a second value, the method comprising the steps of:

• designating one of a plurality of primary operating modes of said control system with a first portion of said bits, wherein each of the primary operating modes has a corresponding state of said first portion of bits selected such that no single bit transition of any of said first portion of bits between said first value and said second value results in a state corresponding to another of said primary operating modes;
• designating one of a plurality of module operating modes for at least one of said sub-modules with a second portion of said bits, wherein each of the module operating modes has a corresponding state of said second portion of bits selected such that no single bit transition of any of said second portion of bits between said first value and said second value results in a state corresponding to another of said module operating modes;
• and
• designating one of said plurality of sub-modules with a third portion of said bits, wherein each of the plurality of sub-modules has a corresponding designator of said third portion of bits selected such that no single bit transition of any of said third portion of bits between said first value and said second value results in a state designating to another of said sub-modules, wherein each of the primary operating modes, module operating modes and sub-modules are designated such that no error produced by any contiguous sequence of four bits results in an erroneous primary operating mode, module operating mode or sub-module transition.

A control system comprising a control module and a plurality of sub-modules, wherein the control module is configured to exchange data with each of the plurality of sub-modules using a data structure comprising a plurality of bits, wherein each of the bits is capable of representing at least a first value or a second value, the data structure comprising:

• a first data field configured to represent a plurality of system modes of the control system with a first portion of said bits, wherein each of the system modes has a corresponding state of said first portion of bits selected such that no single bit transition of any of said first portion of bits between said first value and said second value results in a state corresponding to another of said system modes;
• a second data field adjacent to the first data field and configured to represent a plurality of sub-modes with a second portion of said bits, each sub-mode corresponding to an operating mode for at least one of said sub-modules, wherein each of the sub-modes has a corresponding state of said second portion of bits selected such that no single bit transition of any of said second portion of bits between said first value and said second value results in a state corresponding to another of said sub-modes;
• and
• a third data field adjacent to the second data field and configured to represent a designation for each of said sub-modules with a third portion of said bits, wherein each of the designations has a corresponding state of said third portion of bits selected such that no single bit transition of any of said third portion of bits between said first value and said second value results in a state corresponding to another of said designations;
• wherein the data structure is further arranged such that each of the bit mappings used to represent the system modes, sub-module operating modes and sub-module designators are selected such that no error produced by any single bit nor any contiguous sequence of four or eight bits results in an erroneous system mode, subsystem designation or sub-mode transition.