![Geehy SEMICONDUCTOR APM32F405 Series User Manual Download Page 127](http://html1.mh-extra.com/html/geehy-semiconductor/apm32f405-series/apm32f405-series_user-manual_573630127.webp)
www.geehy.com Page 126
Direct memory access (DMA)
Introduction
DMA (Direct Memory Access) can realize high-speed data transmission
between peripheral devices and memory or between memory and memory
without CPU intervention, thus saving CPU resources for other operations.
The product has two DMA controllers, with 16 data streams. Each data stream
corresponds to 8 channels, but each data stream can only use 1 channel at the
same time. Each data stream can set priority, and the arbiter can coordinate the
priority of corresponding DMA requests of each data stream according to the
priority of the data stream.
Main characteristics
Two DMA; each DMA has 8 data streams, and each data stream has 8
channels
Dual AHB main interfaces; one is memory interface, and the other is
peripheral interface
There are three data transmission modes: peripheral to memory,
memory to peripheral, memory to memory
Each data stream has a special hardware DMA request for connection
Support software priority and hardware priority when multiple requests
occur at the same time
Each data stream has 5 event flags and independent interrupts
Support circular transmission mode
The number of data transmission is programmable, up to 65535
The configurable source and target transmission width is byte, half word
or word
Support source and target incremental modes
The configurable burst increment size is single time, 4, 8 or 16 ticks
Functional description
DMA request
If the peripheral or memory needs to use DMA to transmit data, it is required to
first transmit DMA request and wait for DMA approval before data transmission.