IMPROVED METHOD AND APPARATUS FOR TRAPPING UNIMPLEMENTED OPERATIONS IN INPUT/OUTPUT DEVICES

Apparatus and a method by which the flow of DMA-transferable data from an application program to an input/output device using a direct memory access circuit may be halted when the device is unable to respond to DMA-transferable data sent to it. The apparatus includes circuitry for ascertaining whether the input/output device is able to respond to DMA-transferable data transferred to the input/output device, a circuit for storing the DMA-transferable data transferred to the input/output device to which the input/output device is unable to respond, and circuitry for generating a signal to disable immediately the flow of DMA-transferable data to the input/output device and an interrupt to assure that the DMA-transferable data is handled in an expeditious manner.