We tested now the LAN91C96.

It can easy be used with the 8051. Since it need only 4 address lines and have an internal address latch. So it need only 12 lines to the 8051:
AD0 ... AD7, /WR, /RD, INT, ALE.

The remaining 21 port pins are still available for the application.
Since the interrupt output is high active, an 8051 derivate with high active interrupt input should be used, e.g. DS80C320, C505.

The Ethernet can also be used for program download instead of RS232.


Peter