Apparatus and method for supporting multiple interrupt protocols with unequal number of interrupt request signals

A peripheral device capable of generating interrupt request signals compliant with the Industry Standard Architecture (ISA) protocol, and the Peripheral Component Interconnect (PCI) protocol. The peripheral device comprises a signal generator block which selectively generates either the interrupt request signals of the PCI protocol or a set of bits representative of interrupt request signals of the ISA protocol. The set of bits are transferred serially to a converter circuit which generates the interrupt request signals of the ISA protocol based on the bits. The signal generator block generates bits in such a way as to support both pulse mode and level mode interrupt request signals for the ISA protocol.