WEARABLE TECH AND BIOMETRICS


How to Accelerate Peripheral Monitoring in Low Power


 Analog Devices


Abstract


This article explains the use cases, advantages and disadvantages of utilising direct memory access (DMA) in embedded systems programming. The article describes how DMA interacts with peripheral and  operation of CPUs. The article will also introduce the reader to different DMA bus access architectures, and the advantages of each.


One task that is common for embedded systems is managing external input. Managing input can put a lot of unnecessary computational strain on the processor, causing longer periods in active power modes and slow response times. For optimising power, preserving quick responses to events and managing large continuous data transfers, a microcontroller with direct memory access (DMA) may offer the best solution.


Direct Memory Access (DMA) In system applications involving peripherals, there are many points at which a microprocessor can become bottlenecked. For instance, when managing an ADC that is constantly sending data, a processor can be interrupted so often that it struggles to accomplish other tasks. DMA is a method of moving data and minimising processor involvement in large or fast data transactions. You can think of the DMA controller as a coprocessor whose sole purpose is to interact with memory and peripherals. This allows the main processor to successfully manage a greedy peripheral, focus on another task, or even go to sleep and conserve power while data transactions


38 APRIL 2025 | ELECTRONICS FOR ENGINEERS Advantages of Using DMA CPU Time


DMA minimises the need for processor execution and interrupts, decreasing the required CPU time for data transactions.


Wearables with DMA


Power Consumption Using DMA can yield opportunities to minimise power consumption if it allows the processor to sleep during DMA transfers.


Parallel Operation


Depending on the architectural details of the system bus, the processor may be able to execute other operations while peripheral transactions are taking place.


Table 1. Advantages of using DMA


Disadvantages of Using DMA Cost


Complexity


Incorporating a system with DMA requires a DMA controller, and this can make a system more expensive.


While DMA can reduce the frequency of interrupts, it can increase 


Platform Dependence


DMA controllers have differing internal architectures between and within manufacturers and can have different behaviour depending on their native bus access schemes.


Cache Incoherency DMA transactions can cause logical errors to occur by writing to a cached layer of the memory hierarchy. This can be solved by using cache-coherent system architectures or by invalidating cache storage upon DMA completion.


Table 2. Disadvantages of using DMA


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