Image Number 7 for United States Patent #4768189.
Methodology and associated circuitry (131,141-143, 151,152,161,162,171-174,181) are disclosed for achieving contention-free broadcasting over one or more buses interconnecting a plurality of synchronized stations. In broad terms for the multiple bus case, each station that intends to utilize the buses prepares candidate message frames equalling the number of buses. The first candidate message of each station (301), after a first perturbation, is propagated over the first bus (311); also, the second candidate message of each station (302), after a second perturbation, is propagated over the second bus (312); this process occurs for all buses. Then, any station detecting a mismatch between its most recently propagated bit on a particular bus and the state of that bus deactivates further propagation of the candidate message on that bus. To arrive at the correct candidate message revealed by each bus, the inverse of the original perturbation must be applied to the revealed message. Examples of perturbations include an EXCLUSIVE-OR operation with randomly generated numbers, cyclic shift operation, cyclic inversion operation and linear transformation.