Abstract: A bridging device for mapping and demapping Ethernet data packets onto a SONET network includes an Ethernet controller chip set which receives packet data, a SONET framer for a SONET interface, a UTOPIA interface for the SONET framer, and an FPGA (or ASIC) which bridges the UTOPIA interface and a system bus interface of the Ethernet controller. The FPGA is preferably implemented in VHDL software code as several modules: an Ethernet controller interface module, a chunk memory module, a UTOPIA interface module, a microprocessor interface module, and a UTOPIA OUT module. In a transmit mode, the Ethernet controller interface module interfaces with the data and control signals from a thirty-two bit data bus of the Ethernet controller chip set and writes the data to chunk memory implemented in the FPGA. The chunk memory module implements the chunk memory to a programmable size.