Description The 422 is a bus-to-bus adapter that extends the ISA bus of a PC to a card rack of STD bus I/O boards. It has three parts: an ISA board, and STD board, and a set of flat cables to connect the two boards. The 422 makes the STD board appear as additional ISA boards in a PC. Address Decoding The ISA board decodes the high 8-bits of the address bus. All STD bus I/O boards are mapped into a 256-address window in the ISA I/O space. The standard address range for this window is OXO100 to OXO1FF. The window may changed via a PLD on the ISA card. Address Decoding The ISA board decodes the high 8-bits of the address bus. All STD bus I/O boards are mapped into a 256-address window in the ISA I/O space. The standard address range for this window is OXO100 to OXO1FF. The window may changed via a PLD on the ISA card.