Apparatus and method in a network interface device for storing tracking information indicating stored data status between contending memory controllers

摘要

A network interface device includes a random access memory used as a transmit and receive buffer for transmission and reception of data frames between a host computer bus and a packet switched network. The network interface device includes read and write controllers for each of the transmit and receive buffers, where each write controller operates in a clock domain separate from the corresponding read controller. The memory management unit also includes a synchronization circuit that controls arbitration for accessing the random access memory between the read and write controllers. The synchronization circuit determines the presence of a stored frame in the random access memory by asynchronously comparing write counter and read counter values stored in gray code counters, where each counter is configured for changing a single bit of a counter value in response to an increment signal. The determined presence of one or more stored data frames is used to arbitrate storage of tracking information by either the read controller or the write controller into a holding register used to determine a read status for the random access memory.