A 16 MBPS adapter chip for the token-ring local area network

An adaptor chip is described which is the result of a cost-reduction and function-enhancement project that yielded a single CMOS VLSI module capable of performing all major LAN (local area network) adapter functions and supporting a 16-Mb/s data rate. The chip when combined with external PROM and RAM modules, bus drivers, and discrete line interface components, forms a complete token-ring adapter. The protocol handler performs most bit- and byte-level functions required to implement the IEEE 802.5 protocol and contains rate machines which automatically perform frame-transmit and receive operations directly between the network and the adapter RAM. The design of the chip uses a mix of fully custom and standard cell approaches. Two process enhancements were employed in a standard digital process in order to achieve high-performance analog functions: a high-implant thin-oxide capacitor and a low-threshold n-channel transistor.<>