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DMA stands for 4-channel Direct Memory Access. It is specially The following image shows the pin diagram of a DMA controller −. _pin. 3S. Da. Do,. Doack o. DOACK 1. Do,. Figure 1. Block Diagram. Figure 2. Pin Configuration. MO0€. HAO -. HLDA -. PAIORITY. AE SOLVEA. ME WW -. AEN -. ADSTE -. INTERNAL. Bus. MAAK. Figure 1. Block Diagram. Figure 2. Pin Configuration. 2-

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Embedded Systems Interview Questions. This signal is used to demultiplex higher byte address and data using external latch. It is a tri-state, bi-directional, eight bit buffer which interfaces the to the system data diatram. This is active high signal concern dixgram the completion of DMA service. It is specially designed by Intel for data transfer at the highest speed.

Digital Electronics Oin Tests. In the slave mode, they perform as an input, which selects one of the registers to be read or written. This active high signal clears, the command, status, request and temporary registers. It is used for requesting CPU to get the control of system bus. In the Slave mode, it carries command words to and status word from Analog Communication Practice Tests.

Diagraam is the active-low three state signal which is used to write the data to the addressed memory location during DMA write operation. In the slave mode, it is connected with a DRQ input line Then the microprocessor tri-states all the data bus, address bus, and control bus.


Your email address will not be published. It consists of mode set register and status register.

A 4 -A 7 are unidirectional lines, provide 4-bits of address during DMA service. Addressing Modes of In the Active cycle they output the lower 4 bits of the address for DMA operation. Mode set register is programmed by the CPU to configure whereas the status register is oin by CPU to check which channels have reached a terminal count condition and status of update flag.

Programming Techniques using Block Diagram of Programmable Interrupt Contr When the fixed priority mode is selected, then DRQ 0 has the highest priority and DRQ 3 has the xiagram priority among them. This active high signal enables the 8-bit latch containing the upper 8-address bits onto the system address bus. This signal is used to convert the higher byte of the memory address generated by the DMA controller into the latches.

Pin Diagram of | Block Diagram of | Mode Set Register | Status Register

These are the four least significant address lines. These are the four individual channel DMA request inputs, which are used by the peripheral devices for using DMA pon.

It is an active-low bidirectional tri-state input line, which helps to read the internal registers pn by the CPU in the Slave mode. This signal is used to receive the diatram request signal from the output device. Conditional Statement in Assembly Language Program.

How to design your resume? N is number of bytes to be transferred. After reset the device is in the idle cycle. Computer architecture Practice Tests. Interfacing of with Microprocessor Interview Questions. It resolves the peripherals requests.


The update flaghowever, is not affected by a status read operation. These are the active-low DMA acknowledge lines, which updates the requesting peripheral about the status of their request by the CPU. In the master mode, it is used to load the data to the peripheral devices during DMA memory read cycle.

These are used to indicate peripheral devices that the DMA request is granted. These lines can also act as strobe lines for the requesting devices. 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.

Embedded Systems Practice Tests. Diagfam mark will be activated after each cycles or integral multiples of it from the beginning.

Microprocessor – 8257 DMA Controller

It is the low memory read signal, which is used to read the data from the addressed memory locations during DMA read cycles. 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 pinn CPU. These are the four least significant address lines.