Architecture for a multiple port adapter having a single media access control (MAC) with a single I/O port

摘要

A multiple port adapter having a single MAC chip with a single I/O port has reduced logic circuits and I/O pins for transferring data between a host system and a TDM communication system. The MAC chip includes a transmit MAC and a receive MAC, each coupled at one end through the single I/O port to a port multiplexer and at the other end to respective storage registers. The port multiplexer is coupled to each port. Transmit and receive state registers track the state of each port in the transfer of data in the transmit and receive directions through the single I/O port. The storage registers are coupled through a host bus interface to a host bus and to the host system. Control logic is coupled to the storage register to control the transfer of data between the system and the storage registers. A port selector coupled between the multiplexer and the transmit and receive state registers selects ports for transfer of data in succession. On each chip clock cycle, the port selector selects a state machine register to determine the state of the MACs for processing the data and a section of the FIFO's to write or read data for the selected port. At the end of the cycle, the state registers are set and stay set until selected again. The process repeats for each port in a cyclic manner. Once data is accumulated in the receive storage register, control logic reads the data of the host bus. Once space is available in the transmit storage register, the control logic writes data from the host system to the transmit storage register.