Draw and explain block diagram of dma controller pdf
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- External Device Block Diagram
- Direct Memory Access (DMA) in Computer Architecture
- Direct memory access
Direct memory access DMA is a feature of computer systems that allows certain hardware subsystems to access main system memory random-access memory independent of the central processing unit CPU. Many hardware systems use DMA, including disk drive controllers, graphics cards , network cards and sound cards. DMA is also used for intra-chip data transfer in multi-core processors. Similarly, a processing element inside a multi-core processor can transfer data to and from its local memory without occupying its processor time, allowing computation and data transfer to proceed in parallel. DMA can also be used for "memory to memory" copying or moving of data within memory.
External Device Block Diagram
For the execution of a computer program, it requires the synchronous working of more than one component of a computer. Usually, processors control all the process of transferring data, right from initiating the transfer to the storage of data at the destination. This adds load on the processor and most of the time it stays in the ideal state, thus decreasing the efficiency of the system. DMA controller transfers data with minimal intervention of the processor. The term DMA stands for direct memory access.
Direct Memory Access (DMA) in Computer Architecture
It handles all the input-output operations of the computer system. Input or output devices that are connected to computer are called peripheral devices. These devices are designed to read information into or out of the memory unit upon command from the CPU and are considered to be the part of computer system. These devices are also called peripherals. For example: Keyboards , display units and printers are common peripheral devices. Interface is a shared boundary btween two separate components of the computer system which can be used to attach two or more components to the system for communication purposes.
Fig Block diagram of DMA Controller. Fig DMA Control Operation. DMA Operation: Direct Memory Access involves transfer of data between I/O devices.
Direct memory access
Data Bus D 0 -D 7 : These are bi-directional tri-state signals connected to the system data bus. When CPU is having control of system bus it can access contents of address register, status register, mode set register, and a terminal count register and it can also program, control registers of DMA controller, through the data bus. During DMA cycles these lines are used to send the most significant bytes of the memory address from one of the. In the idle cycle they are inputs and used by the CPU to address the register to be loaded or read. In the Active cycle they output the lower 4 bits of the address for DMA operation.
For the execution of a computer program, it requires the synchronous working of more than one component of a computer. Usually, processors control all the process of transferring data, right from initiating the transfer to the storage of data at the destination.