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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Pin Diagram of Microcontroller. The four least significant lines A 0 -A 3 are bi — directional tri — state signals.
Microprocessor 8257 DMA Controller Microprocessor
Instruction Set of Microprocessor. This is active high signal concern with the completion of DMA service. MARK always occurs at all multiplies of cycles from the end of the data block.
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.
Then the microprocessor tri-states all the data bus, address bus, and control bus. Input Output Interfacing Microprocessor. During DMA cycles i. Digital Logic Design Practice Tests.
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.
In the master mode, it is used to read data from the peripheral devices during a memory write cycle.
In the slave mode, they act as an input, which selects one of the registers to be read or written. It is a tri-state, dlagram, eight bit buffer which interfaces the to the system data bus. It is an active-low chip select line.
These are bidirectional, data lines which are used to interface the system bus with the internal data bus of DMA controller. Your email address will not be published. It is an active-low chip select line.
This signal is used to convert the higher byte of the memory address generated by the DMA controller into the latches. 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. Leave a Reply Cancel reply Your email address will not be published.
Computer architecture Practice Tests. Interfacing of with Block Diagram of Programmable Interrupt Contr Input Output Transfer Techniques. This active high signal enables the 8-bit latch containing the upper 8-address bits onto the system address bus.
Embedded Systems Practice Tests. Analogue electronics Interview Questions. It is an active-high asynchronous input signal, which helps DMA to make ready by inserting wait states. A 4 -A 7 are unidirectional lines, provide 4-bits of address during DMA service.
This signal is used to convert the higher byte of the memory address generated by the DMA controller into the latches. Sample and Hold Circuit.
Microprocessor DMA Controller
82557 In the Slave mode, command words are carried to and status words from Making a great Resume: In the Active cycle they output the lower 4 bits of the address for DMA operation.
It consists of mode set register and status register. Digital Electronics Interview Questions. In master mode, it is used to send higher byte address A 8 -A 15 on the data bus. The most significant 2 bits of the terminal count register specifies the type of DMA operation to be performed. Microcontrollers Pin Description.
In the slave mode, it is connected with a DRQ input line The active high Hold Acknowledge from the CPU indicates that it has relinquished control of fiagram system bus.