Abstract: A serial network interface unit which uses indirect addressing to access an exchange table. In one embodiment, the serial network interface unit comprises a serial communications transceiver, a transmit controller, a receive controller, and a register file for storing an exchange table and an index table. The exchange table has slots for storing information about data exchanges, and the index table has an entry for each ongoing exchange to indicate which of the slots is storing information about the exchange. The transmit and receive controllers are coupled to the register file to reference the index table to determine an exchange table slot corresponding to a current exchange and to thereafter update information in the current exchange table slot. A processor may be coupled to the register file via an i/o bus to store inactive (but ongoing) data exchange information to system memory and to replace the inactive data exchange information with information for active data exchanges.