System for the asynchronous transporting of data between active

Abstract

For mutual bidirectional communication, two active functional units are connected by a bidirectional data bus line and one unidirectional control line for each of the two directions. Both active functional units are each time connected, via an output circuit, to the relevant single connections of the data bus line. The output circuits have at least one first state in order to produce per first state, at a low impedance, a first data state on the connection, and one second state for generating, at a high impedance, a second data state for the connection. When such a first and a second data states are simultaneously present on one and the same connection, the former state dominates. The second state can thus also act as an inactive state. A bidirectional data transport cycle for the first active functional unit includes the following steps: supplying data--transmitting a request signal--detecting an acknowledge signal--deactivating the transmitted data--changing over to the receive state--terminating the receive state--transmitting the acknowledge signal.