Nios® V Processor Software Developer Handbook

ID 743810
Date 7/20/2023
Public

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3.4.3.3.4. Direct Memory Access Devices

The HAL Direct Memory Access (DMA) model uses DMA transmit and receive channels. A DMA operation places a transaction request on a channel. A DMA peripheral can have a transmit channel, a receive channel, or both. This section describes three hardware configurations for a DMA peripheral and shows how to activate each kind of DMA channel using the HAL memory access functions.

The DMA peripherals are initialized by the alt_sys_init() function call and are automatically enabled by the niosv-bsp command.

DMA Configuration and Use Model

The following examples illustrate use of the DMA transmit and receive channels in a system. The information complements the information available in Using DMA Devices. Regardless of the DMA peripheral connections in the system, initialize a transmit channel by running the alt_dma_txchan_open() function, and initialize a receive DMA channel by running the alt_dma_rxchan_open() function. The following sections describe the use model for some specific cases.