SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
The DMA_SYSTEM controller supports external DMA requests through the dma_evt[4:1] pins (see Table 16-1). A logical channel can be configured to respond to an external synchronization request.
Pin Name | DMA_CROSSBAR Input | Signal Name | I/O(1) | Description | Module Reset Value |
---|---|---|---|---|---|
dma_evt1 | DMA_CROSSBAR_2 | EXT_SYS_DREQ_0 | I | External DMA request 0 (system expansion) | Z |
dma_evt2 | DMA_CROSSBAR_3 | EXT_SYS_DREQ_1 | I | External DMA request 1 (system expansion) | Z |
dma_evt3 | DMA_CROSSBAR_167 | EXT_SYS_DREQ_2 | I | External DMA request 2 (system expansion) | Z |
dma_evt4 | DMA_CROSSBAR_168 | EXT_SYS_DREQ_3 | I | External DMA request 3 (system expansion) | Z |
Figure 16-2 shows an example of how to use the external hardware DMA request pins in the DMA_SYSTEM environment.
An external device can use the external DMA request pins to start a logical channel transfer over the general-purpose memory controller (GPMC) interface. The transfer can be a memory-to-memory transfer in which the source memory is in the external device.
By default, the external DMA request signals are not available on external pins after a cold reset. For more information about multiplexing out the two signal lines to pins, see Pad Configuration Registers in the Control Module.
All 127 DMA request lines are transition sensitive.
For a transition-sensitive DMA request (see Figure 16-3), the line must be maintained low (asserted) until the first DMA access is complete, after which the line must be maintained high (deasserted) for greater than one clock cycle (DMA_L3_GICLK):