Q. What do you mean by Daisy chain?

This scheme provides a hardware poll. With this scheme, an interrupt acknowledge line is chain by different interrupt devices. All I/O interfaces share a common interrupt request line. When processor senses an interrupt it sends out an interrupt acknowledgement. This signal passes via all I/O devices till it gets to requesting device. First device that has made interrupt request so senses signal and responds by putting in a word that is generally an address of interrupt servicing program or a unique identifier on data lines. This word is also called as interrupt vector. This address or identifier in turn is used for selecting an appropriate interrupt-servicing program. Daisy chaining has an in-built priority scheme that is determined by sequence of devices on interrupt acknowledge line.