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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These are the active low DMA acknowledge output lines.

As said earlier, it indicates which channels have reached a terminal count condition and includes the update flag described previously. In master mode it is used for chip select. It is active low ,tristate bloco ,Bidirectional lines. It is an active-high asynchronous input signal, which helps DMA to make ready by inserting wait states.

Microprocessor – 8257 DMA Controller

These are the asynchronous peripheral request input signal. In the slave mode, it is used to transfer data between microprocessor and internal registers of When the fixed priority mode is selected, then DRQ 0 has the highest priority and DRQ 3 has the lowest priority among them. When the rotating priority mode is selected, then DRQ0 will get the highest priority and DRQ3 will get the lowest priority among them.

It is cleared by the RESET input, thus disabling all options, inhibiting all channels, and preventing bus conflicts on power-up. In the master mode, the lines which are used to send higher byte of the generated address are sent to the latch.


It is acknowledgment signal from microprocessor. Address Strobe It is a control output line. This signal is used to receive the hold request signal from the output device. Sample and Hold Circuit.

While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. These are active low tri-state signals.

Microprocessor 8257 DMA Controller Microprocessor

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This is active high signal concern with the completion of DMA service. Your email address will blck be published. Interrupt Structure of Digital Logic Design Practice Tests. Automatic visitor based room light controller. Survey Most Productive year for Staffing: Have you ever lie on your resume? 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 used for requesting CPU to get the control of system bus. In the master mode, it also helps in reading the data from the peripheral devices during a memory write cycle.


Microprocessor DMA Controller

Low level indicate that ,peripheral is selected for giving the information DMA cycle. Digital Electronics Interview Questions. Your Duties as a Data Controller. In the Active cycle they output the lower 4 bits of the address for DMA operation. In the master mode, it is used to read data from the peripheral devices during a memory write cycle. These are active low bi-directional signals. This signal is used to demultiplex higher byte address and data using external latch. It containsControl logic Mode set register and Status Register.

Used to clear mode set registers and status registers A0-A3: Most significant four bits allow four different options for the Pin Diagram of 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.

Embedded Systems Practice Tests. In the master mode, they are the four least significant memory address output lines generated by 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. Modular Safety Integrated Controller.

Pin Diagram of and Microprocessor.

This signal helps to receive the hold request signal sent from the output device. It consists of mode set register and status register.