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Tristate lines in the context of the DMA 8257 refer to the control lines that can be in one of three states: high, low, or high impedance (floating). This high impedance state allows multiple devices to share the same bus without interfering with each other, as it effectively disconnects the device from the bus when it is not actively transmitting data. The tristate feature is crucial for managing data transfers between the CPU and peripherals in a system, enabling efficient communication and minimizing conflicts.
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What 8257 chip means?
The 8257 is a three channel DMA controller.
What is the use of Intel 8257 microprocessor?
Its a Programmable Direct Memory Access (DMA) controller.
What is auto load in 8257 DMA controller?
Auto load in the 8257 DMA controller refers to a feature that allows the DMA controller to automatically load the address and count registers from a specified memory location after each DMA transfer. This capability enables the controller to perform multiple transfers without requiring the CPU to intervene between each operation. By using auto load, it simplifies the programming of DMA operations, particularly for repetitive data transfers. This feature is useful in applications where continuous data movement is needed, such as in audio or video processing.
Why A0 to A3 lines are bidirectional in 8257?
The A0 to A3 lines in the 8257 DMA controller are bidirectional because they are used for both address and data transfer. During the address phase, these lines carry the address of the memory location being accessed, while during the data transfer phase, they transmit the actual data. This dual functionality reduces the number of required pins on the chip, making it more compact and efficient in managing data transfers between memory and peripherals.
What is difference between 8237 and 8257 DMA controllers?
8237 provides better performance, compared to 8257. The distinctive feature of 8237 chip is that it provides, many programmable control and dynamic reconfigurability features which enhance the data transfer rate of the system remarkably
Block diagram of 8257 dma controller?
it is a device to transfer the data directly between io device and memory without through the cpu so it performs a high-speed data transfer between memory and io device
What is the gcf of 32511 and 8257?
The GCF is 1
What are the release dates for The Young and the Restless - 1973 1-8257?
The Young and the Restless - 1973 1-8257 was released on: USA: 7 November 2005
Why are the read and write control lines in a DMA controller bi-directional?
The read and write control lines in a DMA (Direct Memory Access) controller are bi-directional because they need to facilitate communication in both directions between the DMA controller and the memory or peripheral devices. When the DMA controller is transferring data from memory to a device, it uses the read line, while the write line is used when transferring data from the device to memory. This bi-directional capability allows the DMA to efficiently manage data transfers without needing to constantly request CPU intervention, thereby improving overall system performance.
What is the tristate area of New York?
The "tristate area" of New York consists of New York, New Jersey and Connecticut.
What is 2881 plus 5376?
2881 + 5376 = 8257
Microprocessor of 8257 dma controller?
8527 DMA controllerThe 8527 controller has four independent channels each of which contains an address register and a counter. The counter decrements as each byte transfer occurs, and forces termination of the DMA operation after the last transfer. The controller increments the address register after each operation, so that successive data transfers are made at contiguous ascending addresses.The arbiter resolves conflicts among the channels for access to memory. Two methods have been used in this chip to make the chip useful in a variety of different applications. In one mode the channels have a fixed priority and conflicts are resolved according to the priority, for example, Channel 0 has highest priority and Channel 3 lowest. The second mode is a rotating priority scheme in which priority rankings are the four cycle shifts of 0-1-2-3, when a channel is granted access to the bus the priority ranking shifts cyclically to place the channel in the lowest priority position for the next arbitration cycle.Structure of the 8527 DMA controllerThe chip has four signals associated with the READ and WRITE operation. MEM READ L and MEM WRITE L are signals produced by DMA controller to exercise memory. The two signals I/O READ L and I/O WRITE L are bidirectional, they are inputs from the microprocessor when the microprocessor sends commands to the 8257 and reads back the 8257 status. During the I/O operation these signals are output from the 8257 and are functionally opposite to the memory signals. The 8257 takes control of the bus by exercising HALT (HRQ) and receives back the "go-ahead" signal on HALT ACKNOWLEDGE (HLDA).Two signals produced by the DMA controller can be used by the I/O port to assist in controlling the transfer process. One signal TC--terminal count--is asserted during the last cycle of a DMA block. This can be used to describe a DMA mode on an I/O port or to reset the port's internal state to indicate the end of a transfer. The second--MARK--is inserted when the remaining count on a channel became a multiple of 128--providing a convenient timing signal for an external device.Block DiagramPin ConfigurationThree Transaction Methods for Peripheral IOs:• Programmed IOs (like 8255 port used without handshake and Intr signals)• Interrupt Driven IOs (like 8255 port used without handshake and Inter signals)• DMA Transactions using a DMACDirect Memory Access Control (Peripheral Transactions Server) IOs· Controller or server sends hold request for processor to grant on acknowledgement, the access to address and data buses, IORD, IOWR, MEMRD, MEMWR and IO buses.· Once programmed for address of RAM block for transfer and for data counts of IO transactions with RAM, interrupts only at the end of a block transaction or last transaction.8257 Four Channel DMAC Features:· Four channels,· Priority Resolution support,· TC output and Mark output (after 126 bytes transfer) for interrupts to processor for attention,· Auto-load on TC mode support for repeat transactions without reprogramming TC and MAR and mode,· TTL level inputs/outputs compatible with INTEL families.
