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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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. Each channel can perform certain specific actions i. It produces MARK signal to the peripheral device that bytes have been transferred.
It requires a single phase clock. Its frequency ranges from Hz to 3MHz. It performs operations in 2 modes, i. When the rotating priority mode is selected, then DRQ0 will get the highest priority and DRQ3 will get the lowest priority among them.
These lines can also act as strobe lines for the requesting devices. In the Slave mode, command words are carried to and status words from In the master mode, the lines which are used to send higher byte of the generated address are sent to the latch. IOR It is an active-low bidirectional tri-state input line, which helps to read the internal registers of by the CPU in the Slave mode. In the master mode, it also helps in reading the data from the peripheral devices during a memory write cycle.
In the master mode, it is used to load the data to the peripheral devices during DMA memory read cycle. CLK It is a clock frequency signal which is required to perform internal operation of In the slave mode, they perform as an input, which selects one of the registers to be read or written. In the master mode, they are the outputs which contain four least significant memory address output lines produced by CS It is an active-low chip select line.
HRQ This signal helps to receive the hold request signal sent from the output device. In the slave mode, it is connected with a DRQ input line MEMW It is the active-low three state signal which is used to write the data to the addressed memory location during DMA write operation.
MARK The mark will be activated after each cycles or integral multiples of it from the beginning. Vcc It is the power signal which is required for the operation of the circuit. Post navigation.
Direct memory access with DMA controller 8257/8237
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.
INTRODUCTION AND ARCHITECTURE OF DMA CONTROLLER 8257 PDF
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.