PROGRAMMABLE DMA CONTROLLER – INTEL It is a 40 pin IC and the pin diagram is, The functional block diagram of is shown in fig. mode set register, and a terminal count register and it can also program, control registers of DMA controller, through the data bus. Pin Diagram of Outputs. The Intel is a 4-channel direct memory access (DMA) controller. It is specifically designed . Block Diagram Showing DMA. Channels.

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It is an active-low chip select line. Most significant four bits allow four different options for the Pin Diagram of It is low ,it free and looking for a new peripheral.

Microprocessor 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. It resolves the peripherals requests. In the slave mode, it is connected with a DRQ input line Analogue electronics Interview Questions. In update cycle loads parameters in channel 3 to channel 2. Block Diagram of Programmable Interrupt Contr Modular Diagrxm Integrated Controller.

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Microprocessor 8257 DMA Controller Microprocessor

Mode set register is programmed by the CPU to configure whereas the status register is read by CPU to check which channels have reached a terminal count condition and status of update flag. Digital Electronics Practice Tests.

This active high signal enables the 8-bit latch containing the upper 8-address bits onto the system address bus. Embedded Systems Practice Tests. In the slave mode, they act as an input, which selects one of the registers to be read or written.


It is used to set the operating modes. The four least significant lines A 0 -A 3 are bi siagram directional tri — state signals. These are bi-directional tri-state signals connected to the system data bus. Addressing Modes of In master mode, it is used to send higher byte address A 8 -A 15 on the data bus. It is a tri-state, bi-directional, eight bit buffer which interfaces the to the system data bus.

It is an active-low chip select line. It is active low ,tristate ,buffered ,Bidirectional control lines. This signal is used to demultiplex higher byte address and data diagrwm external latch. Address Strobe It is a control output line.

These lines can also act as 857 lines for the requesting devices. The mark will be activated after each cycles or integral multiples of it from the beginning. In the Slave mode, controllee words are carried to and status words from It is high ,it selected the peripheral. It is active low ,tristate ,buffered ,Bidirectional lines. It is designed by Intel to transfer data at the fastest rate. A0-A3 bits of memory address on the lines.

These are the four least significant address lines. It is used for requesting CPU to get the control of system bus. Diavram, for N number of desired DMA cycles it is necessary to load the value N-1 into the low order bits of the terminal count register. The TC status bit, if one, indicates terminal count has been reached for that channel.

PPT – DMA Controller PowerPoint Presentation – ID

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It is the active-low three state signal which is used to write the data to the addressed memory location during DMA write operation. It is a write only registers. During DMA cycles these lines are used to send the most significant bytes of the memory address from one of the. It is an active-low bidirectional tri-state input line, which is used by the CPU to read internal registers of in the Slave mode.


It is the active-low three state signal which is used to write the data to the addressed memory location during DMA write operation. The active high Hold Acknowledge from the CPU indicates that it has relinquished control of the system bus. In the active cycle IOR signal is used to access data from a peripheral and IOW signal is used to send data to the peripheral.

Microprocessor – 8257 DMA Controller

It can be programmed to work in two modes, either in fixed mode or rotating priority mode. When the fixed priority mode is selected, then DRQ 0 has the highest priority and DRQ 3 has the lowest priority among them.

Least significant four bits of mode set register, when set, enable each of the four DMA channels. Top 10 facts why you need a cover letter? Loading SlideShow in 5 Seconds. Microprocessor Interview Questions. Embedded Systems Interview Questions.

It is necessary to load count for DMA cycles and operational code for valid DMA cycle in the terminal count register dontroller channel is enabled.