Slide 38 of 53
This slide illustrates the priority implemented in the Bus Resolution Function Protocol. The simplest case to consider (and the only one that will be used in the following example) is for a point-to-point connection in which one element serves as the token source and the other serves as the token sink. In this case, the status of the output token for the source will be either Present or Released, and the status of the output token for the sink will be either Acked or Removed.
The circle in the slide above serves two related purposes. First, note that at any one time, the arrows at the “corners” indicate the four possible states in which the two token drivers can be. For any of these four conditions, protocol will select the token that is at the head of the arrow.
The second purpose of the circle is to illustrate the sequence of token status conditions that will be seen by an observer on the signal connecting the two elements during a communication.