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Abstract

A method for transfer of data between multiple tasks in a host computer and multiple tasks in an intelligent controller. One or more memory buffers for holding the data to be transferred are allocated to each task. Each connection between corresponding tasks in the host and the controller is provided with a set of queues for controlling access by the controller to the memory buffers. An output queue contains descriptions of output buffers holding data for transfer from the host to the controller. A buffer queue contains descriptions of input buffers available for transfer of data from the controller to the host, a return queue contains descriptions of output buffers available for transfer of data from the host to the controller, and an input queue contains descriptions of input buffers holding data that has been transferred from the controller to the host. The queues contain pointers to extended control blocks, each containing a virtual data pointer and a physical data pointer to a specified buffer. When data is to be transferred, a description of a selected buffer is provided to the controller. When the controller has resources available, the host is notified and a description of the selected buffer is provided to the host. The host maps the selected buffer to an I/O segment of virtual memory, and the transfer of data is performed through the I/O segment. After completion of the data transfer, the description of the buffer is placed on the appropriate queue for reuse in a subsequent data transfer.

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