A bus is a collection of wires that connect several devices within a computer system. When a word of data is transferred between units, all its bits are transferred in parallel. A computer must have some lines for addressing and control purposes.
Three main groupings of lines:
1. Data Bus. This is for the transmission of data.
2. Address Bus. This specifies the location of data in MM.
Control Bus. This indicates the direction of data transfer and coordinates the timing of events during the transfer.
Single Bus Structure
All units are connected to a single bus, so it provides the sole means of interconnection. Single bus structure has advantages of simplicity and low cost.
Single bus structure has disadvantages of limited speed since usually only two units can participate in a data transfer at any one time. This means that an arbitration system is required and that units will be forced to wait.
Only two units can actively use the bus at any given time. Bus control lines are used to arbitrate multiple requests for the use of the bus.
Buffer Registers are used to hold information during transfers.
Two Bus Structure
In the first configuration, the processor is placed between the I/O unit and the memory unit. The processor is responsible for any data transfer between the I/O unit and the memory unit. The processor acts as a “messenger.” In this structure, the processor performance and capability is not being maximized. Most of the time, the processor is doing data transfer between these units instead of performing more complex applications. Also, the processor is idle most of the time waiting for these slow devices.
In the second configuration, I/O transfers are made directly to or from the memory. A special purpose processor called peripheral processor or I/O channel is needed as part of the I/O equipment to control and facilitate such transfers. This special processor is the direct memory access(DMA) controller. It allows main memory to perform data transfer between I/O units.
Kantipudi saisandeep on December 05, 2018:
Very useful thanks
Bhavya bayyareddy on May 28, 2018:
Thq very much....it is very helpful fr my study
Athira on June 29, 2017:
thank you. it is very usefull for my study. i also need about the system soft ware
evans on December 06, 2016:
Aswini adumbil on September 28, 2016:
susmita on August 20, 2016:
Prince Hari on April 24, 2015:
Mang Kanor on November 16, 2014:
Thank you for the information , IT will help me for my Research
mick on November 16, 2014:
micky on December 04, 2013:
awesome.... short sweet and simple
sandeep hegde on November 15, 2013:
lokesh8gmail.comm on October 28, 2013:
nita bhandekar on October 24, 2013:
it is very easy notes
Anu on October 18, 2013:
for more info regarding bus structures........
amala on August 04, 2013:
temesgen oljera on June 22, 2013:
anju on March 05, 2013:
sweety on January 13, 2013:
all right guys i am happy to atten my test without having refernce books by having this notes
Sathish on December 26, 2012:
it's very easy to understand
deepak singh on December 17, 2012:
it's very easy
sonali on December 06, 2012:
laxma reddy on October 30, 2012:
seth on October 02, 2012:
shosha on September 22, 2012:
thanks 4 the information it's very useful
jazmine on September 10, 2012:
its very useful!
anjit on September 08, 2012:
nice and fantastic
zeeshan on August 23, 2012:
udu on August 21, 2012:
Menchu on August 21, 2012:
YES! Now I know.... :PPP
cheza akoo on August 21, 2012:
now i know.... :))))
A.kanyakumari on July 20, 2012:
not enough this content but easy to understand
mallemkondaiah on July 07, 2012:
simply to understand
sssh on June 29, 2012:
well...is very easy!
ravi on June 25, 2012:
it s very easy to understand
vicky on June 16, 2012:
very nice indeed.this will help me a lot.........god blesss you
Ali Hakim on May 26, 2012:
khyati on May 14, 2012:
very easy to understand and very helpful to me.thanks a lot.
Priya on May 06, 2012:
It is very useful and easy to understand
aparajita on May 01, 2012:
priyadarsini on March 27, 2012:
very excellent nice,simple,tremindious ,no 1 description for all.after reading this my confidence is very highly increase.
Ajithkumar on March 24, 2012:
it is very useful.thanksss...
fariha jahan on March 10, 2012:
wow!! i got it..
Anil reddy on February 28, 2012:
spoorthy on February 20, 2012:
balaji shinde on February 19, 2012:
sandy on February 18, 2012:
It is very easy to understand....thanks.
Sameer on February 16, 2012:
Excellent,explaind in simple words.Nyc.
tanvi on January 16, 2012:
PAUL NEWMAN on January 11, 2012:
saranya on January 02, 2012:
easy to understand
this force me to learn more.
Rejie on December 05, 2011:
it is very useful for students like me, thanks! ^_^
cath on December 04, 2011:
nice!now i understand..:)
cath on December 04, 2011:
nice!now i understand..:)
aly on December 04, 2011:
karthik on November 27, 2011:
jasmine kaur on November 13, 2011:
sindhu on November 11, 2011:
diljale on October 30, 2011:
arunmaireddy on October 28, 2011:
it is easy to understand nice
anees on October 16, 2011:
Pradeep kumar on October 12, 2011:
Ya fine.. Its very easy to understand.. Very simple defi n explainations..
fathima on September 13, 2011:
it is usefull to us... & it's easy to understand...
ravi on September 13, 2011:
Ashutosh Kumar on July 22, 2011:
very usefull,, if possible make it more detailed.... thnx.
milind on January 03, 2011:
what if we make uch a line that function as both address ine controll line data line