Secure Digital Card Direct Memory Access Support
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8/28/2008
The following table outlines the four types of DMA implementation recommended by the SD Host Controller Specification.
| Term | Description |
|---|---|
No DMA |
SD Host Controller does not support DMA. |
Single operation DMA (SDMA) |
Introduced in version 1.0 of the SD Host Controller Specification. |
Advanced DMA 1 (ADMA1) |
Introduced in version 2.0 of the SD Host Controller Specification, ADMA1 supports data transfer of only 4kB aligned data in system memory. |
Advanced DMA 2 (ADMA2) |
Introduced in version 2.0 of the SD Host Controller Specification, ADMA2 supports data of any location and size in system memory. |
Beginning with Windows Embedded CE 6.0 R2, the Microsoft SD standard host controller supports SDMA and No-DMA host controller implementations. If you are using a proprietary SD host controller driver you can refer to the Microsoft SD standard host controller driver implementation for help modifying your own. DMA support enables client drivers to use the DMA APIs provided by the SD card DDK for better throughput. The DMA interfaces provide a good abstraction layer so that client drivers can take advantage of SD host controller hardware specific DMA capabilities without having to change.