Icera, Inc.

Andrew Glyn Bond

Peter Cumming

Colman Hegarty

Coleman Hegarty

A circuit comprising: an execution unit; a plurality of addressable devices; and a data transfer engine coupled to the execution unit and to the devices, operable to fetch a plurality of descriptors under control of the execution unit, and based on each of the fetched descriptors to perform a transfer of data from a respective first to a respective second of the devices. The DMA engine comprises delay circuitry operable to block, during a delay period running from an earlier of the transfers, any later of the transfers involving at least one of the same devices as the earlier transfer, the delay circuitry being arranged to control the blocking in dependence on an indication received in one of the descriptors.

Data transfer engine with delay circuitry for blocking transfers

Disclosed herein is a method of accessing a slave device from a circuit including a central processing unit, a data transfer engine, and an interface to the slave device. In one embodiment, the method includes: executing code on the central processing unit to set up the data transfer engine to access the slave device; and based on the set-up, operating the data transfer engine to supply a read request word to a transmit buffer of the interface for transmission to the slave device, and, after return of a corresponding response word to a first-in-first-out receive buffer of the interface, to disable the first-in-first-out receive buffer from receiving any further data such that the last word therein is assured to be the response word. The method further includes using an underflow mechanism of the first-in-first-out receive buffer to determine the last word therein and hence determine the response word.

DMA engine

A circuit and corresponding method for transferring data. The circuit comprises: a CPU; a plurality of addressable devices; and a DMA engine coupled to the CPU and to those devices, the DMA engine comprising a plurality of DMA contexts each having fetch circuitry for fetching a DMA descriptor indicated by the CPU and transfer circuitry for transferring data from one to another of the devices based on a fetched descriptor. The DMA engine further comprises switching means operable to control a group of the contexts to alternate in a complementary sequence between fetching and performing a transfer, such that alternately one or more contexts in the group fetch while one or more others perform a transfer.

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Redland, United Kingdom

Andrew Glyn Bond