What are the features of 8237 DMA controller?

What are the features of 8237 DMA controller?

Key Features:

• 24-bit length address register.
• 16-bit length count register.
• 4 independent DMA channels.
• 4 clock / 1 bus cycle.
• Byte transfer / word transfer selectable.
• Supports three transfer modes (Single, Demand, Block)
• DMA request Maskable on an individual channel basis.
• Software DMA request in uPD1037 mode.

Which method is used by 8237 DMA controller?

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.

How is DMA controlled?

The DMA controller sends Hold request (HRQ) to the CPU and waits for the CPU to assert the HLDA. Then the microprocessor tri-states all the data bus, address bus, and control bus. The CPU leaves the control over bus and acknowledges the HOLD request through HLDA signal.

What are the elements of DMA controller?

A DMA controller can generate memory addresses and initiate memory read or write cycles. It contains several hardware registers that can be written and read by the CPU. These include a memory address register, a byte count register, and one or more control registers.

What are the modes of operation of 8237?

The 8237 works in two modes i.e., master and slave modes. In slave mode, the 8237 functions as an input/output device. In this mode the system buses arc controlled by microprocessor and hence the microprocessor is connected to the system bus.

How many DMA channel are there in 8237?

8237 Software Commands Enables all four DMA channels.

What is a DMA controller?

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.

How many types of data transfer is possible with 8237?

Under all these transfer modes, the 8237 carries out three basic transfers namely, write transfer, read transfer and verify transfer. In write transfer, the 8237 reads from an I/O device and writes to memory under the control of IOR and MEMW signals.

What is a DMA operation?

Direct memory access (DMA) is the process of transferring data without the involvement of the processor itself. It is often used for transferring data to/from input/output devices. A separate DMA controller is required to handle the transfer. The controller notifies the DSP processor that it is ready for a transfer.

What is A0 A3 in 8237 used for?

A0 ±A3 Input/Output In the Idle cycle they are inputs and are used by the CPU to address the register to be loaded or read. In the Active cycle they are outputs and provide the lower 4 bits of the output address.

How many DMA codes are there?

210 DMA regions
A DMA region is a group of counties and zip codes that form an exclusive geographic area in which the home market television stations hold a dominance of total hours viewed. There are 210 DMA regions, covering the entire continental U.S., Hawaii, and parts of Alaska.

What is DMA targeting?

Using DMA for Mobile Advertising In addition to more relevance, DMA targeting allows app marketers to target ads toward optimal geographical areas. In order to fully take advantage of DMA targeting, app marketers should conduct DMA analysis throughout the campaign duration.

Who controls the buses in DMA data transfer?

The HLDA signal is a bus grant signal which indicates that the microprocessor has indeed released control of its buses by placing the buses at their high-impedance states. The 8237 DMA controller supplies the memory and I/O with control signals and memory address information during the DMA transfer.

What is the function of Adstb?

ADSTB signifies address strobe which is an active high output pin performing the same function to output of 8085. In Intel 8257, if there is output on this pin as 0, if it is in the slave mode.

How are DMAs defined?

A designated market area (DMA), also referred to as a media market, is a region of the United States that is used to define television and radio markets. There are 210 DMAs covering the whole United States and are usually defined based on metropolitan areas, with suburbs often being combined within.