INTRODUCTION AND ARCHITECTURE OF DMA CONTROLLER 8257 PDF

It is specially designed by Intel for data transfer at the highest speed. Then the microprocessor tri-states all the data bus, address bus, and control bus. Each channel has bit address and bit counter. Data transfer of each channel can be taken up to 64kb. Each channel can be programmed independently.

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It is a programmable; 4-channel, direct memory access controller. Each channel can be programmed individually. Each channel includes a bit DMA address register and a bit counter. DMA address register gives the address of the memory location and counter specifies the number of DMA cycles to be performed. As counter is bit, each channel can transfer 16 kbytes without intervention of microprocessor.

It maintains the DMA cycle count for each channel and activates a control signal TC Terminal count to indicate the peripheral that the programmed number of DMA cycles are complete. It has priority logic that resolves the peripherals requests. The priority logic can be programmed to work in two modes, either in fixed mode or rotating priority mode. It provides inhibit logic which can be used to inhibit individual channels. It allows data transfer in two modes : burst mode and cycle steal single byte transfer mode.

Auto load Features of permits repeat block or block chaining operations. It operates in two modes : slave and master. Extended write mode of prevents the unnecessary occurrence of wait states in the Features of ; increasing the system throughput.

It can be interfaced with all Intel It transfers one byte of data in four clock cycles. Updated: April 4, — pm Related Posts.

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Direct memory access with DMA controller 8257/8237

It is designed by Intel to transfer data at the fastest rate. Then the microprocessor tri-states all the data bus, address bus, and control bus. Each channel has bit address and bit counter. Each channel can transfer data up to 64kb.

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Introduction of 8237

The , on behalf of the devices, requests the CPU for bus access using local bus request input i. HOLD in minimum mode. Internal Architecture of The internal architecture of is shown in figure. The chip support four DMA channels, i.

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Architecture/Functional block diagram of 8257 DMA controller

It is a programmable; 4-channel, direct memory access controller. Each channel can be programmed individually. Each channel includes a bit DMA address register and a bit counter. DMA address register gives the address of the memory location and counter specifies the number of DMA cycles to be performed. As counter is bit, each channel can transfer 16 kbytes without intervention of microprocessor.

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Microprocessor - 8257 DMA Controller

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