A channel time-out apparatus in a data processing system having a channel processor for controlling the allocation of a plurality of input/output channels. The channel time-out apparatus comprises a clock for generating time indications, an address generator for generating an address for each input/output channel of the plurality of input/output channels, a time-out generator for generating a time-out indicator for an input/output channel whenever that input/output channel processes an instruction, storage for storing the last time-out indicator generated by the time-out means for each input/output channel and a comparator for comparing the last time-out indicator stored in the storage for the input/output channel whose address is presently being generated by the address generator with a time indicator presently being generated by the clock for determining when a time-out event has occurred without requiring intervention by the processor.

An apparatus and method for processing channel time-out for input/output channels in a data processing system. A counting device is provided which cycles through a count indicative, in a first part, of each of a plurality of channels in the data processing system and, in a second part, a sequence of time indications. A time indication is saved for a particular channel upon the execution of an instruction for that channel and subsequent comparisons are made of the stored time indication and the present time indication to determine if a difference in these two time indications is sufficient to constitute a time-out.

An apparatus includes an input/output (I/O) address verification unit that determines whether an I/O address received from a processor is protected. An interrupt generator is coupled to the I/O address verification unit. The interrupt generator generates an interrupt if the I/O address is protected. An interrupt recorder is coupled to the address verification unit. The interrupt recorder records a cause of the interrupt.