One also finds many many of the industrial I/O boards that are fitted to ISA or PC-104 bus carrying 82C55's for purposes of the support of parallel I/O. Many of these even have the industry standard DC-37 connector in the bracket for cabling of 3 ports of I/O (24 bits) to an OPTO-22 rack.

Of course these days these vendors now push their daisy chained RS485 "smart I/O controllers" which in all likelyhood have 8051 derivative type parts in them.

Michael Karas