Monday, January 23, 2012

Definition of: feature size

Definition of: feature size 

The size of the elements on a chip, which is designated by the "DRAM half pitch." The smallest feature size is generally smaller than the feature size for a technology generation (technology node). For example, the 180 nm technology generation will have gate lengths smaller than 180 nm.

Definition of: DRAM half pitch 

The common measure of the technology generation of a chip. It is half the distance between cells in a dynamic RAM memory chip. For example, in 2002, the DRAM half pitch had been reduced to 130 nm (.13 micron). By 2006, it had shrunk to 65 nm (.065 micron).

Saturday, January 21, 2012

Download the admit card of UPSC CDS(Combined Defence Services Examination) 2012 (I)

Unlike past, from 2012 onwards  candidates will be able to download their exam admit card at UPSC website. Yes, you heard it. From now on even UPSC admit card will be available online.

Though little late but it seems that even UPSC is learning that it is much better to upload admit card on Internet, rather than sending it by post or asking the candidates to visit UPSC office physically for duplicate hall ticket. A press note which has appeared in The Times of India, main paper and not in Ascent has confirmed the same.




To Download Combined Defence Services Examination admit card  Click  here 

http://upsc.nic.in/onlineadmitcard/main.aspx for 12.02.2012 exam.



tags: upsc admit cards,CDS Hall Tickets ,CDS Admit cards, download   admit card  of UPSC CDS,

Sunday, January 15, 2012

Tech Info :How an Optical Mouse Works

Optical mice are the de facto standard for mice to communicate between the end user and the computer. The optical mouse is a great improvement of the mechanical mouse that was created in the early 1970s.

Agilent Technologies introduced the Optical mouse in 1999. The technology uses a tiny camera that takes thousands of pictures per second to determine position and speed.

The optical mouse uses a very small light emitting diode more commonly referred to as an LED, which is red in color. This LED bounces light off of a mouse pad or desk surface onto a CMOS (Complimentary Metal Oxide Semiconductor).

Friday, January 13, 2012

Russia says about its spacecraft may crash into Atlantic..........!

Russia's space agency has adjusted its forecast for the crash of a failed spacecraft, saying it may shower its fragments into the south Atlantic.

Roscosmos said the unmanned Phobos-Ground probe could plummet to Earth Sunday or Monday anywhere along a broad swath between 51.4 degrees north and 51.4 degrees south.

It said Friday that the mid-point in the two-day window would have the craft crashing into the ocean about 400 kilometers (250 miles) east of the coast of Chubut province in southern Argentina. It said the precise time and place of the uncontrolled plunge can only be clarified later as the probe draws closer to Earth.

At 13.2 metric tons (14.6 tons), the Phobos-Ground is one of the heaviest pieces of space junk ever to plummet to Earth, with highly toxic fuel accounting for the bulk of its weight.

source:http://www.philstar.com/Article.aspx?articleId=767782&publicationSubCategoryId=200

Sunday, January 8, 2012

AWK :The for statement

The for Statement

The for statement makes it more convenient to count iterations of a loop. The general form of the for statement looks like this:

for (initialization; condition; increment)   body 

This statement starts by executing initialization. Then, as long as condition is true, it repeatedly executes body and then increment. Typically initialization sets a variable to either zero or one, increment adds 1 to it, and condition compares it against the desired number of iterations.

Here is an example of a for statement:

awk '{ for (i = 1; i <= 3; i++)           print $i }' 

This prints the first three fields of each input record, one field per line.

In the for statement, body stands for any statement, but initializationcondition and increment are just expressions. You cannot set more than one variable in the initialization part unless you use a multiple assignment statement such as x = y = 0, which is possible only if all the initial values are equal. (But you can initialize additional variables by writing their assignments as separate statements preceding the forloop.)

awk '{ for (i =j= 1; i <= 3; i++)

{if (j <2){

  j++;

        print $i

}

}'


The same is true of the increment part; to increment additional variables, you must write separate statements at the end of the loop. The C compound expression, using C's comma operator, would be useful in this context, but it is not supported in awk.

Most often, increment is an increment expression, as in the example above. But this is not required; it can be any expression whatever. For example, this statement prints all the powers of 2 between 1 and 100:

for (i = 1; i <= 100; i *= 2)   print i 

Any of the three expressions in the parentheses following the for may be omitted if there is nothing to be done there. Thus, `for (;x > 0;)' is equivalent to `while (x > 0)'. If the condition is omitted, it is treated as true, effectively yielding an infinite loop (i.e., a loop that will never terminate).

In most cases, a for loop is an abbreviation for a while loop, as shown here:

initialization while (condition) {   body   increment }

source:http://www.staff.science.uu.nl/~oostr102/docs/nawk/nawk_toc.html#TOC77

Tuesday, January 3, 2012

Vacancy : Project Scientist vacancy in NIOT

National Institute of Ocean Technology (NIOT) Chennai has been
established as the technical arm of the Ministry of Earth Sciences
(MoES), Government of India with the objective of promoting technology
development in various mission mode activities related to Ocean
Engineering and Ocean Resources exploitations. NIOT invites
applications for the following on  contract basis :

Project Scientist – III : 01 post, Pay : Rs. 47300 – 52600
Project Scientist – II : 31 posts, Pay : Rs. 45500 – 50500
Project Scientist – I : 83 posts, Pay : Rs. 43300 – 48100


How to Apply : Apply Online at NIOT website from 03/02/2012 to 10/02/2012.


For more information and application format etc., please visit

 http://www.niot.res.in/recruit/cv/job.php?id=106

10th Class Social Studies - Model Question Paper

                                                                                 SSC- 10th Class Social Studies Paper 2- Model Question Paper

Tenth Class / SSC students are gearing up for the public examinations. With the approaching of March, the 10th Class students crave for model papers and previous question papers. Here we are giving Social Studies Model Paper for the benefit of 10th Class students. There are two parts in Paper - II and the model question paper is for English Medium students. Telugu Medium candidates also can easily understand the questions. Here is the question paper:

SSC Social Studies Model Paper - Paper -II ( Parts - A and B ) (English Version)
Time: 2:30 Hours - Max. Marks: 50

Part - A : Time: 2 Hours - Marks : 35 

SECTION - I

i) Answer ANY FIVE of the following questions, choosing at least TWO from each Group. ii) Each question carries TWO marks. 5 × 2 = 10

GROUP - A

1) What is the need for irrigation development in India ?
2) "The transport and Communications are the life lines of a country" How?
3) Give the important advantages of Mumbai to become the largest port in India ?
4) Why is India called a 'Sub Continent' ?

GROUP - B

5) What are Organised and Unorganised sectors ?
6) What are ' Basic Industries' give examples.
7) Differentiate Cost-push and Demand-pull inflations.
8) Describe the role of private sector in Indian Industrialization? Is it still relevant?

SECTION - II

i) Answer ANY FOUR questions in one or two sentences. ii) Each question carries ONE mark. 4 × 1 = 4
9) List out the atomic minerals.
10) What is meant by population Density?
11) What are the features of red soils?
12) What is the basic reason for the inequality of income?
13) Define 'Poverty line'.
14) Why was the planning Commission established in 1950?

SECTION - III

i) Answer ANY FOUR of the following questions, choosing TWO from each Group. ii) Each question carries FOUR marks. 4 × 4 = 16

GROUP - A

15) Describe the ecological and economic significance of forests
16) What are the problems faced by Indian agriculture?
17) Compare and contrast the coastal plains of East and West.
18) What are the favourable factors for the development of cotton textiles in and around Mumbai and Ahmedabad centres?

GROUP - B

19) Describe the role of banking and financial institutions in india.
20) What were the features of Indian economy during british period?
21) What are the merits and demerits of Indian five year plans ?
22) What are the factors causing regional imbalances ? Explain the indicators of regional disparities.

SECTION - IV

23) Mark the following on the outline map of India. 1 × 5 = 5

SET - A
1) Cochin port 2) Kolleru lake 3) Hiracud project 4) A place where spices are plentifully available 5) Railway line between Kolkata and Chennai (via) Visakhapatnam
OR
SET - B
1) Varanasi 2) K2 peak 3) Puduchcheri 4) 82 1/2 ο E longitude 5) NH4.

Part - B : Time: 30 Minutes - Marks - 15

Choose the correct answer and write the corresponding CAPITAL LETTER in the bracket. 10 × 1−2 = 5
1) Biggest State in India in terms of area- ( )
A) Rajasthan B) Madhya Pradesh C) Maharashtra D) UP
2) Older Alluvium in India is called- ( )
A) Babhar B) Khadar C) Terai D) Bhangar
3) The place which receives the highest rainfall- ( )
A) Shillong B) Masinram C) Cochin D) Trivendrum
4) These soils are deficient of free carbonates- ( )
A) Laterite B) Black Cotton C) Alluvial D) Red
5) The H.Q. of North Eastern Railway Zone is at- ( )
A) Gorakhpur B) Malegaon C) Dispur D) Itanagar
6) East India company captured political power in- ( )
A) 1600 AD B) 1757 AD C) 1700 AD D) 1657 AD
7) Income came through Labour and Work is called- ( )
A) Unearned Income B) Earned Income C) National Income D) Per Capita Income
8) This country has highest adult literacy rate- ( )
A) India B) Pakistan C) China D) Republic of Korea
9) 'Health for All' is now changed as- ( )
A) Rajiv Arogyasri B) Health for Under Previleged C) Health for Rich D) Rural Health Programme
10) 'Heavy Industry Strategy' was the main objective of- ( )
A) First Five Year Plan B) Second Five Year Plan C) Third Five year Plan D) None of the above

II. Fill in the blanks. 10 × 1−2 = 5

11) India gets bulk of its rainfall from -- monsoon.
12) -- Trees are well grown in Tidal forests.
13) -- states records the lowest density (in 2001).
14) Tanks are more in -- state in India.
15) The single largest item of Indian imports is --
16) The firms operating under the government are known as --
17) In -- unemployment the marginal productivity is zero or negative.
18) The life expectancy in India is -- years.
19) The present scheme to fulfil the housing needs is known as --
20) Achieving -- was the chief objective third Five Year Plan.

III. Match the following. 10 × 1−2 = 5

SET - A

GROUP - A : GROUP - B
21) Buckingham Canal ( ) a) Delhi
22) Silk Industry ( ) b) Tamilnadu
23) Cosmopolitan City ( ) c) Odisha
24) Heaven on the earth ( ) d) Speedy Transport
25) Paradeep ( ) e) Navigation
f) Andhra Pradesh
g) Karnataka
h) Srinagar

SET - B

GROUP - A : GROUP - B
26) Small land holdings ( ) a) Primary Sector
27) Plantations ( ) b) H.Y.V. Seeds
28) Green Revolution ( ) c) Industrialisation
29) Basic Industry ( ) d) Problem of Agriculture
30) Means of Communications ( ) e) Machine Tools
f) Tertiary Sector
g) Petroleum Products
h) Iron and Steel.


Read more: http://www.apcollegeadmissions.com/2012/01/ssc-10th-class-social-studies-paper-2.html#ixzz1iPeKtN00

Monday, January 2, 2012

Definition of Metastability...

source:
space.gif

 ../images/main/bullet_green_ball.gif Definition of  Metastability :


Whenever there are setup and hold time violations in any flip-flop, it enters a state where its output is unpredictable: this state is known as metastable state (quasi stable state); at the end of metastable state, the flip-flop settles down to either '1' or '0'. This whole process is known as metastability. In the figure below Tsu is the setup time and Th is the hold time. Whenever the input signal D does not meet the Tsu and Th of the given D flip-flop, metastability occurs.

  

space.gif



../images/tidbits/setup_hold_ff.jpg
  

space.gif



When a flip-flop is in metastable state, its output oscillate between '0' and '1' as shown in the figure below (here the flip-flop output settles down to '0') . How long it takes to settle down, depends on the technology of the flip-flop.

  

space.gif




  

space.gif



If we look deep inside of the flip-flop we see that the quasi-stable state is reached when the flip-flop setup and hold times are violated. Assuming the use of a positive edge triggered "D" type flip-flop, when the rising edge of the flip-flop clock occurs at a point in time when the D input to the flip-flop is causing its master latch to transition, the flip-flop is highly likely to end up in a quasi-stable state. This rising clock causes the master latch to try to capture its current value while the slave latch is opened allowing the Q output to follow the "latched" value of the master. The most perfectly "caught" quasi-stable state (on the very top of the hill) results in the longest time required for the flip-flop to resolve itself to one of the stable states.

  

space.gif



../images/tidbits/meta_hill_dia.gif
  

space.gif

 ../images/main/bullet_green_ball.gif How long does it stay in this state?


The relative stability of states shown in the figure above shows that the logic 0 and logic 1 states (being at the base of the hill) are much more stable than the somewhat stable state at the top of the hill. In theory, a flip-flop in this quasi-stable hilltop state could remain there indefinitely but in reality it won't. Just as the slightest air current would eventually cause a ball on the illustrated hill to roll down one side or the other, thermal and induced noise will jostle the state of the flip-flop causing it to move from the quasi-stable state into either the logic 0 or logic 1 state.

  

space.gif




  

space.gif

 ../images/main/bullet_green_ball.gif What are the cases in which metastability occurs?


As we have seen that whenever setup and hold violation time occurs, metastability occurs, so we have to see when signals violate this timing requirement:

  

space.gif



  • When the input signal is an asynchronous signal.
  • When the clock skew/slew is too much (rise and fall time are more than the tolerable values).
  • When interfacing two domains operating at two different frequencies or at the same frequency but with different phase.
  • When the combinational delay is such that flip-flop data input changes in the critical window (setup+hold window)
  

space.gif

 ../images/main/bullet_green_ball.gif What is MTBF?


MTBF is Mean time between failure, what does that mean? Well MTBF gives us information on how often a particular element will fail or in other words, it gives the average time interval between two successive failures. The figure below shows a typical MTBF of a flip-flop and also it gives the MTBF equation. I am not looking here to derive MTBF equation :-)

  

space.gif



../images/tidbits/meta.h2.gif










































Normally,

  

space.gif



  • We can use a metastable hardened flip-flop
  • Cascade two or three D-Flip-Flops (two or three stages synchronizer).
  

space.gif

 ../images/main/bullet_green_ball.gif METASTABILITY REFERENCES
  

space.gif



  • http://www-s.ti.com/sc/psheets/sdya006/sdya006.pdf
  • Thomas J. Chaney, "Measured Flip-Flop Responses to Marginal Triggering", IEEE Transactions on Computers, Vol. C-32. No. 12, December 1983, pp.1207-1209.
  • Lindsay Kleeman and Antonio Cantoni, "On the Unavoidability of Metastable Behavior in Digital Systems", IEEE Transactions on Computers, Vol. C-36. No. 1, January 1987, pp.109-112.
  • Lindsay Kleeman and Antonio Cantoni, "Can Redundancy and Masking Improve the Performance of Synchronizers?", IEEE Transactions on Computers, Vol. C-35, No. 7, July 1986, pp.643-646.
  • Cypress Semiconductor, "Are Your PLDs Metastable?, Fax ID: 6403, May 1992, Revised March 6,1997. http://www.cypress.com/pld/pldappnotes.html#pldmeta
  • http://www.xilinx.com/apps/xapp.htm
  • M. Valencia, M. J. Bellido, J. L. Huertas, A. J. Acosta, and S. Sanchez-Solano, "Modular Asynchronous Arbiter Insensitive to Metastability. IEEE Transactions on Computers, 44(12):1456-1461, December 1995

Setup and hold times of an flip-flop

Setup and hold times

Setup time is the minimum amount of time the data signal should be held steady before the clock event so that the data are reliably sampled by the clock. This applies to synchronous circuits such as the flip-flop.

Hold time is the minimum amount of time the data signal should be held steady after the clock event so that the data are reliably sampled. This applies to synchronous circuits such as the flip-flop.

To summarize: Setup time -> Clock flank -> Hold time.

The metastability in flip-flops can be avoided by ensuring that the data and control inputs are held valid and constant for specified periods before and after the clock pulse, called the setup time (tsu) and the hold time (th) respectively. These times are specified in the data sheet for the device, and are typically between a few nanoseconds and a few hundred picoseconds for modern devices.

Unfortunately, it is not always possible to meet the setup and hold criteria, because the flip-flop may be connected to a real-time signal that could change at any time, outside the control of the designer. In this case, the best the designer can do is to reduce the probability of error to a certain level, depending on the required reliability of the circuit. One technique for suppressing metastability is to connect two or more flip-flops in a chain, so that the output of each one feeds the data input of the next, and all devices share a common clock. With this method, the probability of a metastable event can be reduced to a negligible value, but never to zero. The probability of metastability gets closer and closer to zero as the number of flip-flops connected in series is increased.

So-called metastable-hardened flip-flops are available, which work by reducing the setup and hold times as much as possible, but even these cannot eliminate the problem entirely. This is because metastability is more than simply a matter of circuit design. When the transitions in the clock and the data are close together in time, the flip-flop is forced to decide which event happened first. However fast we make the device, there is always the possibility that the input events will be so close together that it cannot detect which one happened first. It is therefore logically impossible to build a perfectly metastable-proof flip-flop.



Propagation delay

Another important timing value for a flip-flop (F/F) is the clock-to-output delay (common symbol in data sheets: tCO) or propagation delay (tP), which is the time the flip-flop takes to change its output after the clock edge. The time for a high-to-low transition (tPHL) is sometimes different from the time for a low-to-high transition (tPLH).

When cascading F/Fs which share the same clock (as in a shift register), it is important to ensure that the tCO of a preceding F/F is longer than the hold time (th) of the following flip-flop, so data present at the input of the succeeding F/F is properly "shifted in" following the active edge of the clock. This relationship between tCO and th is normally guaranteed if the F/Fs are physically identical. Furthermore, for correct operation, it is easy to verify that the clock period has to be greater than the sum tsu + th.



source:http://en.wikipedia.org/wiki/Flip-flop_(electronics)

India Year Book 2011 is available in English language for download

Now India Year Book 2011 is available in English language for download.

it contains...

  • Economy
  • Science & Technology
  • Society
  • Polity
  • Education
  • Art & Culture


Sunday, January 1, 2012

SETUP TIME & HOLD TIME EQUATIONS for Flip Flop

SETUP TIME & HOLD TIME EQUATIONS

This section derives the equation for valid input window for a flip-flop to avoid set up and hold time violations. 
 

 

Assume tskew = 0, and FF2 is processing IN1, and FF1 is processing IN2,



IN2 should not reach FF2 before thold of FF2 to avoid Meta stability at FF2,

Hold time -> tCQ (FF1) + tcomb > thold (FF2)--- Eq.1

At the same time, IN2 should reach FF2 before setup time of FF2,

Setup time -> tCQ (FF1) + tcomb < tclk - tsetup (FF2)--- Eq.2

If tskew != 0, equations will be modified in the following way,

Hold time -> tCQ (FF1) + tcomb > thold (FF2) + tskew --- Eq.3

Setup time -> tCQ (FF1) + tcomb < tclk + tskew - tsetup (FF2) --- Eq.4

In Eq.3, skew is added to hold time, becomes effective hold time. In Eq.4, skew is added to clock period, becomes effective period or you can think, effective set up time is decreased by skew. This discussion is just for the purpose of our understanding. From equations, positive skew is good for setup time and bad for hold time.