Texas Instruments Corporation

Kyle Castille

Sanjive Agarwala

Quang-Dieu An

Natarajan Kurian Seshan

Hung Ong

Shoban Srikrishna Jagathesan

Clayton Gibbs

Sanjiva Agarwala

Command reordering in the hub interface unit (HIU) of Enhanced Direct Memory Access (EDMA) functions is described. Without command reordering in the EDMA, commands are issued by the HIU to the peripheral in order of issue. If the higher priority transfers are issued later by the EDMA, the previously issued lower priority transfers would block the higher priority transfers. Command reordering in the HIU causes transfers to be reordered and issued to the peripheral based on their priority. Reordering allows the EDMA and HIU to give due service to high priority transfer requests with decreased weight placed on the order in which the requests were issued.

Command re-ordering in hub interface unit based on priority

An enhanced direct memory access (EDMA) operation issues a read command to the source port to request data. The port returns the data along with response information, which contains the channel and valid byte count. The EDMA stores the read data into a write buffer and acknowledges to the source port that the EDMA can accept more data. The read response and data can come from more than one port and belong to different channels. Removing channel prioritizing according to this invention allows the EDMA to store read data in the write buffer and the EDMA then can acknowledge the port read response concurrently across all channels. This improves the EDMA inbound and outbound data flow dramatically.

Concurrent read response acknowledge enhanced direct memory access unit

The present invention provides for independent source-read and destination-write functionality for Enhanced Direct Memory Access (EDMA). Allowing source read and destination write pipelines to operate independently makes it possible for the source pipeline to issue multiple read requests and stay ahead of the destination write for fully pipelined operation. The result is that fully pipelined capability may be achieved and utilization of the full DMA bandwidth and maximum throughput performance are provided.

Independent source read and destination write enhanced DMA

The invention describes a modification of FIFO hardware to allow improved use of FIFOs for burst reading from or writing to a processor direct memory access unit via either an expansion bus or an external memory interface using FIFO flag initiated bursts. The hardware and FIFO signal modifications make the FIFO-DMA interface immune to deadlock conditions and generation of spurious interrupt events in the process of initiating burst transfers. The FIFO function is modified to synchronize the frame transfer on the digital signal processor even if the digital signal processor lacks this functionality. By delaying the programmable flag assertions within the FIFO until after the current burst is complete the DSP-FIFO interface may be made immune to deadlock conditions and generation of spurious events.

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Kyle Castille