A method for communicating between a first system and a second system using a full-duplex synchronous serial link capable of simultaneously routing between both systems is disclosed. The data involved includes at least one message from the first system to the second, at least one message from the second system to the first, and a clock signal. The method involves the second system receiving a message and a clock signal sent by the first system, delayed and substantially in phase, the second system sends a message to the first system, the clock signal received by the second system is sent back to the first system with the message sent by the second system, and the first system receives the message sent by the second system and the sent-back clock signal, delayed and substantially in phase.