A method of operating a communication infrastructure for a data processing apparatus, the communication infrastructure comprising first switching circuitry for coupling to at least one first master interface and at least one first slave interface, second switching circuitry for coupling to at least one second master interface and at least one second slave interface, and a bidirectional link interconnecting said first switching circuitry and said second switching circuitry, the method comprising the steps of:
- employing within said first switching circuitry and said second switching circuitry a multi-channel communication protocol, whereby on initiation of a transaction from an initiating master interface to a target slave interface for the transaction, a communication path is established from said initiating master interface to said target slave interface, the communication path comprising m channels, said m channels comprising one or more forward channels from said initiating master interface to said target slave interface and one or more reverse channels from said target slave interface to said initiating master interface, and handshaking signals being associated with each of the m channels;
- providing a plurality n of connection lines within the bidirectional link, where n is less than 2m;
- arranging the bidirectional link to support a first communication path from the first switching circuitry to the second switching circuitry, and a second communication path in an opposite direction from the second switching circuitry to the first switching circuitry, both the first communication path and the second communication path providing said m channels;
- and
- multiplexing at least one forward channel of the first communication path and at least one reverse channel of the second communication path, such that the 2m channels formed by the first and second communication paths are provided by the n connection lines of the bidirectional link, said multiplexing being performed in dependence on the handshaking signals associated with the channels to be multiplexed, wherein the channels of said 2m channels that are multiplexed, and the connection lines that those channels are multiplexed onto, are chosen having regard to one or more predetermined criteria;
- whereby the bidirectional link is employed to form at least part of the communication path for any transaction where the initiating master interface is one of said at least one first master interface and the target slave interface is one of said at least one second slave interface, or for any transaction where the initiating master interface is one of said at least one second master interface and the target slave interface is one of said at least one first slave interface.