MU9C8328

The MU9C8328 speeds up bridging operations using Ethernet controller chips with serial NRZ data outputs, such as AMD's MACE™, National's SONIC™, and Motorola's QUICC™ controllers, by parsing the Ethernet frame independently of the Ethernet controller device, and notifying it whether to accept or reject the incoming frame.

The MU9C8328 supports both positive and negative filtering on the Destination address and learning of new Source addresses, by efficiently controlling the compare activities of the MUSIC LANCAM Family. Filtering and learning routines are user configurable. These routines are automatically invoked by the internal state machine based on the contents of the incoming frame and the configuration settings. For aging and other housekeeping routines, the MU9C8328 provides the proper sequencing and timing of LANCAM accesses for an external processor.

The MU9C8328 receives serial NRZ data from the Ethernet controller chip, finds the Start delimiter, and loads the DA and SA into registers. The DA is sent to the LANCAM for filtering and, depending on the filter action selected, notifies the controller whether to copy or purge the frame. The SA is then sent to the LANCAM for comparison, and if no match is found, can be learned to the Next Free address in the LANCAM. Scheduling is done within the MU9C8328 so that each filtering action completes in the time of a minimum length frame. The filtering and learning routines are preprogrammed in the MU9C8328, with decision options set in the control register. A Status register is provided so the host processor can determine the results of activities. The specific Op-Code for the LANCAM learning instruction is by default a MOV NF, CR, V, but it can be overridden by writing a value to the Op-Code register. Aging and purging activity is directly controlled by the host processor. The READY signal notifies the host processor that processor operations are complete. The / INT signal notifies the processor that a network frame has been processed and the result stored in the Status register. The processor can turn off the network filtering activity to have total control of the LANCAM; during this time the controller can be notified to accept or reject all frames.