Chapter 9

Direct Memory Access (DMA)

Many devices can temporarily take control of the bus. These devices can perform data transfers that involve main memory and other devices. Because the device is doing the work without the help of the CPU, this type of data transfer is known as direct memory access (DMA). The following types of DMA transfers can be performed:

• Between two devices

• Between a device and memory

• Between memory and memory

This chapter explains transfers between a device and memory only. The chapter provides information on the following subjects:

• DMA Model

• Types of Device DMA

• Types of Host Platform DMA

• DMA Software Components: Handles, Windows, and Cookies

• DMA Operations

• Managing DMA Resources

• DMA Windows