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. The hardware device used for direct memory access is called the DMA controller.
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These are the active-low and high inactive DMA acknowledge lines, which updates the peripheral requesting device service about the status of their request by the CPU. These lines can also act as strobe lines for the requesting devices.
Microprocessor Interview Questions. Microprocessor Practice Tests. IT Skills. Management Skills. Communication Skills. Business Skills. Digital Marketing Skills. Human Resources Skills. Health Care Skills. Finance Skills. All Courses. All Practice Tests. It is specially designed by Intel for data transfer at the highest speed. As seen in the above diagram these are the four individual asynchronous channel DMA request inputs, which are used by the peripheral devices to obtain DMA services.
When the rotating priority mode is selected, then DRQ0 will get the highest priority and DRQ3 will get the lowest priority among them. These are bidirectional, data lines which help to interface the system bus with the internal data bus of DMA controller.
In the Slave mode, command words are carried to and status words from In the master mode, the lines which are used to send higher byte of the generated address are sent to the latch. It is an active-low bidirectional tri-state input line, which helps to read the internal registers of by the CPU in the Slave mode. In the master mode, it also helps in reading the data from the peripheral devices during a memory write cycle.
In the master mode, it is used to load the data to the peripheral devices during DMA memory read cycle. These are the four least significant address lines.
In the slave mode, they perform as an input, which selects one of the registers to be read or written. In the master mode, they are the outputs which contain four least significant memory address output lines produced by It is an active-low chip select line. It is an active-high asynchronous input signal, which helps DMA to make ready by inserting wait states. This signal helps to receive the hold request signal sent from the output device. In the slave mode, it is connected with a DRQ input line It is the hold acknowledgement signal which indicates the DMA controller that the bus has been granted to the requesting peripheral by the CPU when it is set to 1.
It is the low memory read signal, which is used to read the data from the addressed memory locations during DMA read cycles. It is the active-low three state signal which is used to write the data to the addressed memory location during DMA write operation. This signal is used to convert the higher byte of the memory address generated by the DMA controller into the latches.
The mark will be activated after each cycles or integral multiples of it from the beginning. Microprocessor Tutorial. Job Recommendation Latest. Jobs in Meghalaya Jobs in Shillong.
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Direct memory access with DMA controller 8257/8237
Suppose any device which is connected at input-output port wants to transfer data to transfer data to memory, first of all it will send input-output port address and control signal, input-output read to input-output port, then it will send memory address and memory write signal to memory where data has to be transferred. In normal input-output technique the processor becomes busy in checking whether any input-output operation is completed or not for next input-output operation, therefore this technique is slow. This problem of slow data transfer between input-output port and memory or between two memory is avoided by implementing Direct Memory Access DMA technique. Suppose a floppy drive which is connected at input-output port wants to transfer data to memory, the following steps are performed:. GeeksforGeeks has prepared a complete interview preparation course with premium videos, theory, practice problems, TA support and many more features.
Direct Memory Access (DMA) in Computer Architecture
These are the active-low and high inactive DMA acknowledge lines, which updates the peripheral requesting device service about the status of their request by the CPU. These lines can also act as strobe lines for the requesting devices. Microprocessor Interview Questions. Microprocessor Practice Tests. IT Skills. Management Skills.