D.M.A. controller that determines whether the mode of operation as either interrupt or D.M.A. via single control line

Year	Description
1998	Invention patented by Helmut Salbaum, Harald Bauer, and Friedrich Fruhwald on June 24th, 1998. Abstract: The invention discloses a communication system for exchanging data between a bus and at least one coupled data processing arrangement via a serial interface which is coupled to a microprocessor by a control line via a DMA unit. For effecting an efficient data exchange between a bus and a serial interface by means of a DMA unit while the controlling microprocessor is slightly loaded, the DMA unit, while in an active state featuring an interrupt mode, is provided for transferring an interface control signal to the microprocessor by the control line and, while in an inactive state featuring a DMA mode, is provided for forming at least one DMA control signal from the interface control signal and for transferring the formed DMA control signals to the microprocessor by the control line. For utilizing a serial interface for a data exchange both in the interrupt mode and in the DMA mode, the control line is looped through by the DMA unit. In the DMA mode, the DMA unit is interleaved with the control line and changes the interface control signals. The control signals directly transferred in the interrupt mode are interpreted and assigned to DMA signals which are then applied to the microprocessor instead.
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Invention: D.M.A. controller that determines whether the mode of operation as either interrupt or D.M.A. via single control line