Introduction to DMA Controller ECE Project:
DMA controller is a device which controls the system to directly transfer the information from one peripheral to another. The controlling is necessary because the data move very fastly even faster than a particle. For example take a black and with picture with 256 and 240 vertical and horizontal dots respectively then the picture is scanned twice that means 60 times every second when this dots are represented double on display. 256×240=61400 bits of information scanning of these bits twice means two microseconds for every bit.
For this process of fetching every time the memory and time also wasted. To avoid all this problems the data should be stored on onboard memory with built in scanning technique. This can be achieved by maintaining a ram and vram. The frame buffer refreshes every time when the data is accessed. DMA takes control over system bus and produces its own address and control’s information of system bus. Due to narrow timing constraints it is not suitable for scanning video for regular display. DMA is used regularly when the picture is transferred from regular memory frame buffer. It gains control over the processor which are using bus. Intel 82357 DMA controller is used to control the transfer services. It has 40-pins. By maintaining several DMA chips together any number channels can be supported.
DMA Data Transfer:
DMA transfer can be triggered in two ways they are
- By Software
- By Hardware
When the process is executing DMA buffer is allocated and hardware is instructed to transfer the data in buffer the hardware writes the data and raises an interrupt and it is received by interrupt handler and it is handled.
The hardware notifies a new data is received. The interrupt handler asks the hardware where to transfer the data. The device writes the data and notifies once again.
Download DMA Controller ECE Project Report.