GD32F20x User Manual
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12.
Direct memory access controller (DMA)
12.1.
Overview
The direct memory access (DMA) controller provides a hardware method of transferring data
between peripherals and/or memory without intervention from the CPU, thereby freeing up
bandwidth for other system functions. Data can be quickly moved by DMA between
peripherals and memory as well as memory and memory without any CPU actions. There are
14 channels in the DMA controller (7 for DMA0 and 7 for DMA1). Each channel is dedicated
to manage memory access requests from one or more peripherals. An arbiter is implemented
inside to handle the priority among DMA requests.
The system bus is shared by the DMA controller and the Cortex™-M3 core. When the DMA
and the CPU are targeting the same destination, the DMA access may stop the CPU access
to the system bus for some bus cycles. Round-robin scheduling is implemented in the bus
matrix to ensure at least half of the system bus bandwidth for the CPU.
12.2.
Characteristics
Programmable length of data to be transferred, max to 65536.
14 channels and each channel are configurable (7 for DMA0 and 7 for DMA1).
AHB and APB peripherals, FLASH, SRAM can be accessed as source and destination.
Each channel is connected to fixed hardware DMA request.
Software DMA channel priority (low, medium, high, ultra high) and hardware DMA
channel priority (DMA channel 0 has the highest priority and DMA channel 6 has the
lowest priority).
Support independent 8, 16, 32-bit memory and peripheral transfer.
Support independent fixed and increasing address generation algorithm of memory and
peripheral.
Support circular transfer mode.
Support peripheral to memory, memory to peripheral, and memory to memory transfers.
One separate interrupt per channel with three types of event flags.Support interrupt
enable and clear.
Support Full_Data transfer mode: when the transfer size of source and destination are
not equal and the transfer size of source is 32-bit, the DMA automatically unpacks the
necessary transfers to optimize the destination transfer size. This feature is only
available for the channel 5 of DMA1.
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