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