Explain functions of direct memory access, Computer Engineering

Assignment Help:

Q. Explain functions of direct memory access?

Though CPU intervention in DMA is minimised however it should use path between interfaces that is system bus. So DMA involves an extra interface on system bus. A scheme known as cycle stealing permits DMA interface to transfer one data word at a time, after that it should return control of bus to processor. Processor merely delays its operation for one memory cycle to permit directly memory I/O transfer to 'steal' one memory cycle. When an I/O is requested processor issues a command to DMA interface by transmitting to DMA interface the subsequent information (Figure below): 

  • Which operations (write or read) to be performed using write or read control lines.
  • Address of I/O devices that is to be used communicated on data lines.
  • Starting location on memory where information will be read or written to be communicated on data lines and is stored by DMA interface in its address register.
  • Number of words which are to be read or written is communicated on data lines and is stored in data count register.

927_Explain functions of direct memory access.png

Figure: DMA block diagram


Related Discussions:- Explain functions of direct memory access

Colour management, There are three primary colours in pigments - Red, Yello...

There are three primary colours in pigments - Red, Yellow and Blue. There are two ways to produce more colours:   Physical Mixing: Physically mix colours to produce a new colour

Binary tree can be converted in to its mirror image, A binary tree can be c...

A binary tree can be converted in to its mirror image By traversing it in Preorder

How are the instructions provided to computer, Let's answer our second ques...

Let's answer our second question first. All computers have a Unit which performs arithmetic and logical functions. This Unit is called as Arithmetic and Logic Unit (ALU). However h

Define the term grade of service, Define the term Grade of Service. Gr...

Define the term Grade of Service. Grade of Service: In loss systems, the traffic carried through the network is usually lower than the actual traffic offered to the network t

Why pointer variable to a function as an argument, Why pointer variable som...

Why pointer variable sometimes desirable to pass a pointer to a function as an argument? Frequently, a called function needs to make changes to objects declared in the calling

Explain lan topologies, Explain LAN Topologies and its basic topologies. ...

Explain LAN Topologies and its basic topologies. LAN Topologies: Network topology is a physical schematic that shows interconnection of the various users. There are four fund

Two ethernet switches sw1 and sw2 , Six machines H1, H2, ..., H6 are linked...

Six machines H1, H2, ..., H6 are linked by two Ethernet switches SW1 and SW2 as given below. Both switches have four ports drawn. The port numbers are as indicated. Suppose the two

Simplify the boolean expression, Simplify the Boolean expression F = C(B + ...

Simplify the Boolean expression F = C(B + C)(A + B + C). Ans. Simplification of the given Boolean Expression F = C (B +C) (A+B+C) given as F = C (B+C) (A+B+C) = CB + CC [(A+B+C

Explain the use of functions in parallel programming, Q. Explain the Use of...

Q. Explain the Use of functions in parallel programming? include "pvm3.h" main() {    int cc, tid, msgtag;    char buf[100];    printf("%x\n", pvm_mytid());

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd