Method and apparatus to determine the timing of a periodically repetitive event with respect to the position of a rotating body, and more particularly ignition timing, fuel injection timing, and the like, in automotive internal combustion engines

System to determine the timing of a periodically repetitive event with respect to a predetermined angular reference position of a rotating body of an apparatus, in which said timing is determined as a function of an operating parameter of the apparatus, the timing of the periodically repetitive event, with respect to said predetermined reference position of the body being controlled by a square wave electrical signal having a leading flank, the time occurrence of which, with respect to said predetermined reference position, is obtained by a first computation,

• and a trailing flank, the time occurrence of which with respect to the leading flank thereof is obtained by a second computation based on the timing of the leading flank with respect to said predetermined reference position,
• said system comprising
• means providing clock control signals
• a transducer means (21) generating a first marker signal related to the predetermined reference position of the body in the apparatus, and further generating a second marker signal relating to rotation of said body over a predetermined angular interval beyond said predetermined reference position;
• and a digital data processing system carrying out said first computation and calculating, during time intervals related to angular intervals of rotation of said body beyond said predetermined reference position, digital electrical control signals having calculated values which are representative, in digital form, of operating parameters related to and characterizing the operation of the apparatus;
• counter and count decode logic means (80, 81) carrying out said second computation and establishing, by timed sequential counting of said clock control signals, in intervals subsequent to said first marker signal, the temporal relationship between the angular position of the rotating body and said event under control of said calculated digital electrical control signals, wherein the digital processing system carrying out said first computation, and the counter and decode logic means (80, 81) counting and thereby carrying out said second computation, are operating simultaneously, independently from each other, and during time overlap;
• and wherein said data processing system and said counter and decode logic means (80, 81) includes
• separate units comprising a main control unit (33);
• an arithmetic unit (32) to carry out all calculations including calculation of the occurrence, in time, of said leading flank and the trailing flank of said square wave electrical signal;
• a data exchange control unit (38);
• an external data memory unit (39) storing the relationship or function between change in operating parameters of the apparatus and the timing of the event;
• a buffer memory unit (38);
• at least one input circuit unit (30, 31);
• at least one output circuit unit (36), the output circuit unit (36) providing a voltage pulse in the form of said square wave electrical signal as a function of the angle of rotation of said body from said predetermined reference and as a function of at least one of said operating parameters of the apparatus;
• and a bus system (41, 42, 43) interconnecting said units (33, 32, 38, 39, 34, 30, 31, 36), said main control unit also controlling selective connection of said external data memory (39) to said bus system to supply data to said bus system, said data exchange unit (38) and said arithmetic unit (32).