kinetis设备怎样配置dma周期触发功能英-HowtoConfigure.PDF

Freescale Semiconductor Document Number:AN4639 Application Note Rev. 0, 12/2012 How to Configure DMA Periodic Trigger Function on Kinetis Devices by: Jimmy Cheng Contents 1 Introduction 1 Introduction1 2 DMA MUX request sources4 The enhanced direct memory access (eDMA) controller is integrated in most of Kinetis families and it performs data 3 Application5 movement operations with high efficiency. Most of the time a 4 Initialization5 user wants to implement data movement operations periodically. This peripheral request may request only a DMA 5 Conclusion7 transfer when the PIT trigger is produced, because the PIT 6 Example code8 trigger works by gating the request form the peripheral to DMA channel until a trigger event has been seen. 7 References9 This application note is aimed at configuring DMA Periodic 8 Glossary9 Trigger mode function. Example code is built on KE15 device. DMA MUX routes 53 peripheral DMA sources/slots and 10 always-on slots to any of the 16 channels. DMA MUX has three operating modes: • Disabled mode: In this mode, the DMA channel is disabled. Because disabling and enabling of DMA channels is done primarily via the DMA configuration registers, this mode is used mainly as the reset state for a DMA channel in the DMA channel MUX. It may also