A data communication device having multiple ports is provided with an auto-negotiation system for performing auto-negotiation with multiple link partners connected to the ports. The auto-negotiation system has a memory and an auto-negotiation unit including transmit, receive and arbitration state machines for performing transmit, receive and arbitration state diagrams compliant with the IEEE 802.3 Standard. The auto-negotiation unit operates in a time-division multiplexing mode using successive time slots for supporting auto-negotiation operations for different ports. The memory is used for storing state diagram variables for a port in a time interval between the time slots assigned to that port.