A Direct Memory Access (DMA) controller can be used to transfer data from a peri

Question

A Direct Memory Access (DMA) controller can be used to transfer data from a peripheral to memory, memory to peripheral and from memory to memory.
Explain the operation of a DMA controller, using the Analog to Digital Converter (ADC) input as an example.

The architecture of the STM32F4xx microcontroller is given in Figure 1. It is based around an ARM Cortex-M4 with a Floating Point Unit (FPU). The microcontroller is self contained, with memory to store the program and variables and a wide range of peripheral devices. The following questions relate to Figure 1. External memory controller (FSMC) SRAM, PSRAM, NOR Flash, data RAM 64 UTAG & SW ETM MPU NMC ARM Cortex-M4 168 MH FPU Flash RNG 1 MB Ethemet MAC 10/100 SRAM 112 KB USB OTG HS SRAM 16 KB USB OTG FS DMA2 as so DMAT VDD Power GPIO PORTA GPIO PORTB GPIO PORT C GPIO PORT D GPIO PORTE GPIO PORTF GPIO PORT G GPIO PORT H GPIO PORT I PORPDR PVD WDG EXT IT, WKUP SDIOMMC TIM1PWM TIMB/PWM ETRA TIM13 USART2 USART3 UART4 TIM9 ? TIM 10 WWDG UART5 SP2/12S2 SP3M2S3 2C1/SMBUS USART1 USARTE TIMT Tamporalure sansor 12C3SMBUS ITF ADC2 DAC2 OACI OUT Figure 1: STM32F4xx Microcontroller Architecture

Explanation / Answer

DMA controller fascilitates int he transfer of data from peripheral registers to memory and vice versa without the intervention of CPU.

If the case of ADC the analog input that is applied to the ADC is converted to its digital equivalent by the ADC.

The Converted result is stored in the ADC Register and an interupt is generated indicating the coversion has been completed.

DMA controller can be programmed to handle this interrupt so that it can transfer the converted value directly to the memory without intervention by CPU and thereby saving valuable cycle/processing time of the CPU.

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