At the heart of Ethernet communications is the TCP/IP protocol. The TCP/IP stack allows total location independence and interoperability to any embedded application. The software stack shown includes the key blocks associated with the network OSI reference model based on IEEE standards. A typical TCP/IP stack requires ~25K bytes of code space depending on the protocols included. With the 128Kb of code space available on the PIC18F97J60 family, a TCP/IP stack can easily be accommodated while leaving plenty of program memory for the application.