What is DMA Why is it necessary explain the internal block of DMA controller 8237?

Intel 8237 is a direct memory access (DMA) controller, a part of the MCS 85 microprocessor family. It enables data transfer between memory and the I/O with reduced load on the system’s main processor by providing the memory with control signals and memory address information during the DMA transfer.

What are some of the issues that you need to worry about when using DMA?

DMA transfers overcome the problem of occupying the CPU for the entire time it’s performing a transfer. DMA can lead to cache coherency problems If a CPU has a cache and external memory, then the data the DMA controller has access to (stored in RAM) may not be updated with the correct data stored in the cache. 3.

What is DMA draw the internal architecture of 8257 DMA and explain its operation in detail?

DMA stands for Direct Memory Access. It is designed by Intel to transfer data at the fastest rate. It allows the device to transfer the data directly to/from memory without any interference of the CPU.

Which of the following command is used to make all the internal registers of 8237 Clear?

master clear command
Explanation: Using master clear command, all the internal registers of 8237 are cleared, while all the bits of the mask register are set.

Which method 8237 DMA controller uses to prioritize the DMA channels?

Rotating Priority Mode- If the RP bit of mode set register is set then the 8237 operates in rotating priority mode. After each DMA cycle, the priority of each channel changes. Hence all channels will get equal opportunity if they are enabled and their DMA requests exist.

What are the features of 8237 DMA controller?

Key Features: 16-bit length count register. 4 independent DMA channels. 4 clock / 1 bus cycle. Byte transfer / word transfer selectable.

What are the three primary conditions that are required for DMA to take place?

Central processing unit.

  • Input output.
  • parallel port.

    • What is DMA controller in computer architecture?

    Direct Memory Access (DMA) : DMA Controller is a hardware device that allows I/O devices to directly access memory with less participation of the processor. DMA controller needs the same old circuits of an interface to communicate with the CPU and Input/Output devices.

    What is DMA controller in architecture?

    What is DMA in computer architecture?

    Direct Memory Access (DMA) is a capability provided by some computer bus architectures that allows data to be sent directly from an attached device (such as a disk drive) to the memory on the computer’s motherboard.

    In which mode more than one 8237 can be connected together?

    Cascade Mode: In this mode, more than one 8237 can be connected together to provide more than four DMA channels.

    When the count becomes zero in the current word register then?

    Explanation: The current word register is a 16-bit register that holds the data transfers. The word count is decremented after each transfer, and the new value is stored again in the register. Explanation: When the count becomes zero, the EOP signal is generated.