Bus Control Methods for Inductive Coupling Interface

A building block type computing system is constructed by stacking various chips three-dimensionally using an inductively coupled wireless communication interface TCI (Through Chip Interface). Vertical buses using TCI have the benefit of forming a multi-drop shared bus among multiple chips. However, it requires magnetic flux to pass between multiple chips, so the diameter of the coil needs to be increased. In a typical shared bus, it is common to provide dedicated signals for arbitration. However, in the case of TCI, the area cost is too high to use a large-diameter coil exclusively for arbitration. Therefore, arbitration must be performed only by detecting data collisions in the TCI bus, and this point is similar to arbitration methods for other wireless buses, which perform arbitration based only on signal collisions. However, TCI is limited in the small scale of the chip stack, and there is a synchronization signal between chips. We take advantage of this feature and use chip IDs to sort the order of data transmission by each chip when a collision occurs within the TCI bus. We propose a Collision Sort method to do this. The proposed method was evaluated with a cycle-level simulation, and it was confirmed that the performance was close to that of the Ideal Shared Bus with a dedicated arbitration bus.