Many 32 uC have DMA, when are they needed controller

[matrixofdynamism]

The purpose of a hard DMA controller is to help with memory transfer of large blocks. The main processor simply instruct the DMA what chunk of data needs to be transferred and then move onto other important things that form part of the main program.

When do people even use a DMA? And how come only high end microcontrollers and microprocessors have a DMA?

 

[shaiko]

When do people even use a DMA?

Whenever they want to save CPU processing time.

And how come only high end microcontrollers and microprocessors have a DMA?

This is somewhat incorrect. Many "low end" cores utilize a DMA.