Port adapter system including a controller for switching channels upon encountering a wait period of data transfer

Claim 1

In a data processing system having a memory, a plurality of peripheral devices and an I/O system coupled to said memory and to said peripheral devices for controlling the transfer of data therebetween, the improvement comprising a port adaptor within said I/O system for transmitting data between said memory and said peripheral devices, said port adaptor comprising: memory interface means coupled to said memory; first and second channels coupled between said memory interface means and said peripheral devices, each channel being coupled to a different peripheral device; and control means including a control store for storing control sequences and sequencing means responsive to said control sequences for controlling and performing said data transfers between said memory interface means and said channel means, said sequencing means permitting only one channel to operate at a time using a control sequence applicable to the currently operable channel; said control store containing control sequences applicable to respective ones of said channels wherein respective control sequences applicable to said channels include wait periods occurring during data transfer operations which the respective channel waits on until the happening of one or more events, said control means being responsive to system interrupt messages from said I/O system for providing concurrent data transfers between said memory interface means and selected peripheral devices via said channels by providing for switching operation from one channel to the other in response to encountering a wait period during the performance of a data transfer operation for said one channel, said sequencing means operating in response to the occurrence of a wait period encountered while performing a control sequence for one channel to alternate its operation to the performance of a control sequence for the other channel, whereby said sequencing means can provide concurrent data transfer operations for said channels to different peripheral devices.