DMA CONTROLLER FOR USB AND LIKE APPLICATIONS

摘要

Various enhancements may be made to a DMA controller (34) to optimize the DMA controller (34) for use in non-uniform DMA applications such as Universal Serial Bus (USB) applications. First, a DMA count register (54) that is used to store a count value that controls the length of a data transfer over a DMA channel (24) may be capable of being selectively disabled, such that when the DMA count register (54) is disabled, a DMA control circuit (38) may perform a data transfer independent of the DMA count register (54). An endpoint watchdog timer (40) may also be coupled to a DMA control circuit (38) and configured to generate an interrupt if no data is received by the DMA channel (24) within a predetermined period of time. In addition, a DMA control circuit (38) may incorporate partial word hold off functionality to delay transmission of a final word of data from a data packet if the final word is a partial word. FUrthermore, a USB profile circuit (26) may be coupled to the DMA control circuit (38) and configured to control at least one operational parameter of the DMA control circuit (38) to selectively optimize the DMA control circuit (38) for use with a selected USB protocol among a plurality of USB protocols supported by the USB profile circuit (26).