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PSoC®3 and PSoC®5 devices feature a Direct Memory Access (DMA) engine, which can used for data transfer between on-chip elements without any CPU intervention. The DMA engine is part of a high performance bus known as the peripheral hub (PHUB). The PHUB is a programmable and configurable central bus backbone within PSoC3/PSoC5 devices that ties the various on-chip system elements together. It consists of multiple spokes; each spoke is connected to one or more peripheral blocks.
The DMA with the help of Transaction Descriptors (TD) can move data from a source to destination at very high speeds. The TDs can be chained together to perform complex data transfers. The following diagram illustrates a simple data transfer using DMA.
The key features of PSoC® 3 and PSoC® 5 DMA are:
- 24 DMA channels
- Each channel has one or more Transaction Descriptors (TDs) to configure channel behavior. Up to 128 total TDs can be defined
- TDs can be dynamically updated
- Eight levels of priority per channel
- Any digitally routable signal, the CPU, or another DMA channel, can trigger a transaction
- Each channel can generate up to two interrupts per transfer
- Transactions can be stalled or canceled
- Supports transaction size of infinite or 1 to 64k bytes
- TDs may be nested and/or chained for complex transactions
Please refer AN52705 - PSoC® 3 and PSoC 5 - Getting Started with DMA for information on different ways to configure the DMA channel and TD to perform data transfers. The application note also has example projects and a brief video.