Backward compatibility for plug and play systems

A backward compatible plug and play device for adaptive use with a computer of either a PNP or a legacy non-PNP type having system data and address busses, said device being coupled to said computer system data and address busses, said device comprising:

• first storage means, coupled to said computer system data bus, for storing an I/O address for the device, wherein said first storage means outputs a default I/O address upon power-up;
• a DMA channel register, coupled to said computer system data bus, for storing a DMA channel value for the device, wherein said DMA channel register outputs a default DMA channel value upon power-up;
• an interrupt level register, coupled to said computer system data bus, for storing an interrupt level value for the device, wherein said interrupt level register outputs a default interrupt level value upon power-up;
• and
• control logic, coupled to said first storage means, said computer system address bus and said computer system data bus, wherein said control logic:
• upon detecting activity on said computer system data bus characteristic of a computer system attempting to assign I/O addresses to a device, disables said device and allowes a computer system to write to said first storage means an I/O address;
• upon detecting activity on said computer system data bus characteristic of a computer system attempting to assign DMA channel value to a device, allows a computer system to write to said DMA channel register a DMA channel value;
• and
• upon detecting activity on said computer system data bus characteristic of a computer system attempting to assign interrupt level value to a device, allows a computer system to write to said interrupt level register an interrupt level value.