The W89C926 PENTIC+ is a CMOS device designed for easy implementation of PCMCIA R2.1 compatible CSMA/CD local area networks. The W89C926 combines a W89C902 Serial LAN Coprocessor for Twisted-pair (SLCT) with a PCMCIA Bus Interface (PBI), thus integrating into a single chip all the registers and logic necessary to connect the SLCT to buffer SRAMs, flash memories (or an EEPROM), and the PCMCIA system bus. The PCMCIA Bus Interface (PBI) is designed to provide a switchless setting architecture that allows the card setting to be configured by software. It implements a full set of PCMCIA registers for PCMCIA R2.1 compatibility and a set of configuration registers for switchless card setting. The card can be configured quickly and easily by modifying the contents of the configuration registers. The PENTIC+ can run with shared memory mode and NE2000TM I/O mode drivers on a 16-bit bus interface. No extra effort is needed to ensure software compatibility. The PENTIC+ provides a flexible flash memory (up to 128 KB)/EEPROM (up to 512 bytes) architecture for PCMCIA nonvolatile storage and an ID/Configuration auto-load architecture for power-on initialization. Vendors can store the Ethernet ID, configuration, and CIS in the flash memory or EEPROM. The PENTIC+ will auto-load necessary information when power is switched on.