Ethical Implications of Cloning and Stem Cell Research Essay Example for Free

Ethical Implications of Cloning and Stem Cell Research Essay Bio-medical breakthroughs in the fields of genetic and tissue engineering hold great promise. However, as modern medicine advances, it often poses major ethical issues on which people are seriously divided. The argument in favor of proceeding with research at unrestrained pace is mainly advocated by scientists and medical experts who would like to see some fantastic therapeutic benefits that science promises in the form of stem cell technologies. Scientists are absolutely thrilled by the possibilities looming on the horizon (Thompson, Harrub 2001c). On the other side of the debate are people, sometimes led by religious groups, who are concerned we may going too far too fast, using unacceptable means and in unknown directions. Stem cell research has the greatest potential for saving lives, but is controversial for its research based on embryos and fetuses (Rickard 2002). Stem cells are immature and unspecialized cells that that possess both the capacity to renew themselves indefinitely as well as the capability to differentiate themselves into specialized and mature cells. Mature cells, such as the heart’s myocytes or the liver’s hepatocytes, stop dividing after several dozen divisions, while stem cells can keep on dividing indefinitely, either renewing themselves or bringing out specialized cells. There are four types of stem cells in the human body 1) adult stem cells, 2) fetal stem cells 3) embryonic stem cells, and 4) nuclear transplant stem cells. For the first three months of pregnancy, a fertilized cell, or zygote, divides and grows in the mothers womb and is referred to as an embryo. The embryo’s stem cells are the precursors of the development of a complete human baby. They produce all of the bodys various 100 trillion cells. It should become possible to use embryonic stem cells to regenerate any type of cell that the body needs. When the embryo assumes an apparent human body form, it becomes a fetus. Because the fetus is growing rapidly, all tissues and organs, including the brain, contain stem cells. It is for this reason that stem cell researchers are interested in studying fetal tissues. Studies suggest that human embryonic stem cells have immense potential in terms of developing into multiple tissue types and long-term self-renewal. Therefore, stem cell research entails the intentional creation of human embryos in the highly artificial context of an IVF clinic, using cloning techniques, and discarding them after their use for research is exhausted (Thompson, Harrub 2001a). The question to be resolved is whether research on embryonic stem cells constitutes a violation of fundamental human rights, in particular the principle of respect for human dignity and the right of life. However, many believe that conception/fertilization is not a moment but a process, and the early development does not indicate true individuality in any sense of the word, and therefore there is violation of human rights. The promise of embryo research, liberal-minded people tend to think, is too real to ignore any longer by sticking to conservative attitudes that stand in the face of pragmatism. And yet, even they would flinch at the possibilities of reproductive cloning. The difference between therapeutic cloning using embryonic stem cells (stem cell research) and reproductive cloning is the distinction between creating cloned body tissue or organs for therapeutic purposes and creating cloned human beings. Reproductive cloning is generally viewed as morally abhorrent because it is seen as unnatural and a commodification of human life, and it captures public fears about the power of science to pursue a eugenic agenda. When governmental organizations of today debate ban on human cloning, the main issue in such debates would be whether to ban outright all forms of embryo cloning, which a number of countries seem to support, or to permit the cloning of embryos for research purposes (therapeutic cloning/ stem cell research) while outlawing human reproductive cloning. Besides reproductive cloning, there is another untoward ramification to therapeutic cloning, which is cloning for enhancement. The issue of using advances in stem cell research for the purposes of enhancement, as against solely therapeutic purposes, opens up a Pandora’s box of all kinds of complications, ethical, social, psychological, philosophical and practical. For instance, stem cell approaches might help to cure Parkinsons patients, but, in the not too distant future, they could also be used to improve brain functions. Rich people would be able to afford this therapy and poor people would not. This could create a most undesirable stratification of the society. But where does therapeutic cloning end, and enhancement cloning begin — even if cloning was advanced for purely therapeutic purposes, it would soon spread into the domain of enhancement. This is the argument of â€Å"slippery slope† commonly advanced against all biomedical research involving genetic and cellular manipulation. Last but not least, thanks to the promise that genetic engineering and human cloning research hold, the prospects of achieving capabilities for indefinite life extension even within the next twenty to thirty years are very high (Thompson, Harrub 2001b). The consequences of physical immortality for whole populations are simply inconceivable. But today, the possibility of human race becoming permanently deathless looms uncomfortably close to us. Therefore it becomes imperative that something be done to stem the advances of genetic and cloning research before the situation goes out of hand. A number of states have already enacted specific cloning-ban legislation, either banning the cloning of humans or imposing a moratorium on cloning within the state. Other states have taken action at least to consider formally similar legislation. At federal level, the Human Cloning Prohibition Act of 2003, which bans the process of human cloning for any purpose and the importation of any product derived from an embryo created via cloning, was passed by the U. S. House of Representatives on 27 February 2003. It was not ratified by the senate though. The Human Cloning Prohibition Act of 2005 bans only reproductive cloning while allowing therapeutic cloning. To date, federal regulations only prohibit federal funding for research into human cloning (Cash 2005). Though the science of bio-medical engineering is making rapid strides, and offers the promise of unveiling radical new therapies, simply the fact that a technology exists does not imply that anyone who can pay for it can be automatically allowed to use it. This is because the emerging genetic and cellular techniques and technologies raise all kinds of issues, ethical, philosophical, social, psychological and so on. They carry with them implications very difficult even to comprehend.

Family Support in Mental Illness

Family Support in Mental Illness Family is an important and inevitable part of an individual and its uninterrupted presence gives us a psychological support and courage to courageously deal with any kind of trouble.It provides a strong and long lasting shelter to a person and every one looks toward his family for primary care. Although family’s role is necessary in physical illness but in psychiatric illness it has an undeniable and imperative part in treatment exercise and it is indeed one of the mental health promoting practice. So we can say that family plays an integral role in alleviating the significance of mental illness because only medical intervention is ineffective. The support of family for an individual with mental illness is crucial in Asian Indian culture. The involvement of the family is so imperative, that often it becomes a prerequisite of seeking help for psychiatric illness (Stanhope, 2002 as cited in Cook Tarnovetskaia, 2008). Studies have concluded that the rate of recovery from schizophrenia is greater and mortality of people with schizophrenia is lower in the developing world than in the developed countries and the key positive factor that bring that change is the involvement of families in the course of treatment (Warner, 2009). Let’s view this aspect in a sense that what difference it will make if family is not involved in the treatment of psychiatric illnesses in cases where people living alone without any family support during the course of their illness. Maladaptive parental behavior is associated with an increased risk in offspring for anxiety, depression, disruptive personality, and substance use disorders during late adolescence and early adulthood. (Ajit Avasthi,2010) Childhood exposure to parental verbal aggression is associated, by itself, with moderate to large effects on measures of dissociation, irritability, depression and anger-hostility.According to studies, lack of family and social relationship cause homelessness and badly effect the quality of life (Pinikahana, Happell, Hope Keks,2009). . This causes too much frustration to the patient and instead of reducing mental illness it enhances much pain and suffering to the patient. Thus it has been found that when family support is absent the severity in the mental disorder keep increasing and any sort of medication often failed to produce good result. Resultantly family support is very vital and has a big impact to a patient suffering from mental illness.. Families have valuable information and knowledge about their relatives. They also have expertise, acquired through sometimes painful experience.They know about approaches that work and those that do not. Consumers, service providers and families beneà ¯Ã‚ ¬Ã‚ t greatly when family members are involved as full partners in the care and support of people with mental health and addiction problems. When family support is not provided to an individual suffering from a mental illness, he endures a lot of setbacks and it has a direct impact on him. Mostly he confused about his parents changed behavior and feels embarrassing for being in the affected persons company. A 50 years old male patient Noor Ali Hussain was in Nizari Senior Citizen, suffering from mental illness for the last ten years. The patient has a history of schizophrenia, bipolar disorder, depression and odd behavior. On clinical day, I interviewed him about his family history. He told me that his family leaves in America and they have left him in senior citizen. Moreover, he explained that his family doesn’t come to meet him, they just call him only on some special occasion. He stated that he feels happy when he talk to family and he want to live with them. However his family doesn’t take him with them to America because he is illiterate and aged.Further stated family told him that we are busy in our work no one is here to take care of you and left me in senior citizen. After carefully assessing this pathetic situation I decided to choose this topic that is family support in mental illness. In my patient multiple disorders were present and in such cases family suppor t is very important in rehabilitation and recovery of mental illness. But, in my patient case, unfortunately the family support ceased to exist. Care giving literature has illustrated that the prominent role in the provision of support for individuals with mental illness falls on family members, especially on women (Saunders 2003, Zauszniewski et al. 2008, Huang et al. 2009). Evidence linking caring for a member with mental illness to increased levels of burden for the family caregiver is compelling and consistent. Family caregivers have widely identified burden as ‘any individual whose presence and performance aroused either fear or shame must be burdensome and could not be living within a supportive environment’ (Thompson Doll 1982, p. 380). Studies have concluded that mostly people consider taking care of a mentally ill person as a burden. The family care giving burden framework best define my patient case because it distinguishes between the objective and subjective burden (Hoening and Hamilton,1996). Objective burden emerge in the form of disruption in everyday life in the household, financial constraint, breakdown in daily activities and social interaction and these are observe by the caregiver. Subjective burden are the caregivers feelings, attitude and emotions that reflects that he carries a burden(Bull, 1990; Hoening Hamilton,1966; MaurinBoyd, 1990; Reinhard, 1994). Therefore it is necessary to minimize the sense of burden felt by caregivers. Some strategies and interventions that could be help when families are involved in order to promote mental health are discussed briefly. Skilled Training and Health Management(STHM) intervention was developed with the aim of enhancing independent functioning and health care outcomes for older adults with SMI (primarily schizophrenia-spectrum disorders and bipolar disorder) (Bartels et al., 2004).moreover HM consisted of health care preventive measures to identify and monitor acute and chronic medical problems. Moreover family interventions should focus on expanding training to patient and key relatives about mental illness recovery, skills training, task sharing of household and self-care. A positive change in these areas is likely to improve the quality of life of people with mental illness and their families. Other effective strategies include discussion, debriefing session and family therapy that are good practices to involve family in care. Family therapy is also useful Psychotherapy that teaches families and their members to resolve the issue effectively and improve their understanding. According to psychiatric mental health nursing book(2006) Psychoeducation family therapy has been more successful in treatment of patient with schizophrenia and it reduces long term hospitalization as well(Dixon, 2001). According to psychiatric mental nursing book(2006),Self-help group are best position to help clients and families find additional support and information. Family support in mental illness can’t be ignored and it has a lasting role in the recovery of a mentally disorder individual. But sometime family considers burden and feels embarrassed and frustrated. In such crucial time, I think nurse can play a positive role by educating and counseling the family and his close relative about the intensity of the case and teach them strategies and skill to tackle the issue. By concluding, it can be said that family is an important source in promoting mental health but at the same time it is also necessary for the care professional to avoid commenting any mistake which may restrain the family from their beloved one who suffer from mental illness.Lastly, through assessing the identified framework and effective strategies we can play a role in alleviating the burden of mental illness that may bring a positive change in the patient who is diagnosed with mental illness. The prerequisite to promote mental health is to deal the patient holisticall y and make family involvement in treatment an integral part.

Gauley Bridge Disaster and Bhopal Disaster

Gauley Bridge Disaster and Bhopal Disaster Accident Causation Gauley Bridge Disaster Industrial disasters were common during the great depression because of the disregard for safety guidelines by contracting companies. Accident causations during this period were mainly the inability by organization to uphold the safety regulations for employees working in hazardous conditions such as silicosis infection as in the case of the Gauley Bridge disaster. The Gauley Bridge disaster is one of the largest industrial disasters in the United States. The disaster occurred in 1930s during the great recession (Corn 132). The project that led to the occurrence of the disaster involved the construction of a hydroelectric generation power in West Virginia. This required the diversion of water of the two rivers in the area to enhance the power generation process (Magnuson 322). The Rinehart and Dennis Company and the New Kanahwa Power Company companies were involved in the construction the tunnel and power plant respectively. The Rinehart and Dennis Company contracted both African-Americans and Caucasians to work in the construction of the tunnel in 1930s. The construction of the tunnel involved drilling through a rock that had a high percentage of silicon. Research indicates that some of the rocks in the area, had approximately 99.3% silicon, which was very hazardous to humans. In addition, the workforce at the tunnel were not provided with the appropriate safety gears and the machinery used contributed to increase in dust from the site (Corn 133). The individuals working at the site were exposed to high levels of silicon from the rock and hence contracted silicosis. The exact number of individuals who died from the disaster was not established by the approximate number provided was 700 individuals; most of whom were African-Americans. The causes of the disaster involved the failure by the company to examine the conditions of the area in terms of silicon percentage in order to employ the appropriate safety mechanisms (Magnuson 324). In addition, the workers were not provided with dust masks which could have reduced the number of deaths as well as silicosis infections. Bhopal Disaster The Bhopal disaster occurred because of the leakage of the methyl isocyanate (MIC) gas from various storage tanks of the Union Carbide factory in India.   The Union carbide factory is located in the region of Madhya Pradesh at Bhopal, India. The methyl isocyanate (MIC) gas is used as an intermediate in the production of pesticides and is produced by mixing phosgene gas with methyl amine. The total amount of gas that was released to the air from the factory is estimated to be 36 tones (Bowonder and Harold 184). The methyl isocyanate gas had various effects on the environment and residents of Bhopal such as chest tightness, burning sensation in the eyes and reduction of levels of oxygen from the environment. This gas accident caused approximately 2500 deaths and caused permanent physical body damage to approximately 17000 individuals. The pollution caused by this disaster continue to affect the residents of Bhopal due to the pollution of water and soils in the surrounding areas (Bowo nder and Harold 190). The causes of the Bhopal disaster were both technical and safety issues. The inappropriate storage of the gas in tanks for long duration violated the safety guidelines. In addition, the location of the factory in a populous neighborhood contributed to the high number of causalities. Other causes include the malfunctioning of the refrigeration units and safety devices at the factory. This accident could have be prevented through the implementation of various safety guidelines such as installation of adequate number of safety devices and the storage of the gas at the right containers based on the safety guidelines (Bowonder and Harold 200). The factory should be located in sparsely populous areas to minimize the number of casualties in case of an accident. Related Accidents or Disasters Triangle Shirtwaist Factory fire: This industrial accident occurred in New York City in 1905. The disaster caused approximately 100 workers through burning and injuries while escaping fire. The disaster was caused by malfunctioning of the machines and failure by the company to uphold safety guidelines on fire. A legislation requiring improved safety guidelines in the industries was established to prevent future accidents. Chicago Crib Disaster: This disaster occurred in 1909 when fire broke out during the construction of a Chicago water intake tunnel. Data indicates that approximately 60 workers died from burns and by drowning in the lake. Various safety legislations have been enacted to ensure the safety of workers as well as installation of appropriate fire escape mechanisms in risky working sites.   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   Works Cited Bowonder, B., and Harold A. Linstone. Notes on the Bhopal accident: Risk analysis and multiple perspectives. Technological Forecasting and Social Change 32.2 (1987): 183-  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   202. Corn, Jacqueline K. Historical aspects of industrial hygiene-II. Silicosis. The American Industrial Hygiene Association Journal 41.2 (1980): 125-133. Magnuson, Harold J. Health hazards in the construction industry. Journal of Occupational and Environmental Medicine 3.7 (1961): 321-325.

Eco-feminism :: essays research papers

â€Å"Women have long been associated with nature.†   Ã‚  Ã‚  Ã‚  Ã‚  In the following essay Judith Plant sets out the main principles (in regards to ecofeminism): the closeness of women to nature; the belief that the domination of women and the destruction of nature have the same root cause; patriarchy; and the need to re-establish for nature the organic metaphor over the machine metaphor.   Ã‚  Ã‚  Ã‚  Ã‚  Judith Plant believes that women have long been associated with nature and that historically, women have had no real power in the outside world, no place in decision-making. Other things such as the intellectual life, the work of the mind, have traditionally not been accessible to women for many reasons. Some of these reasons have included society’s mentality. According to Judith, today, ecology speaks for the earth, and feminism speaks for the ‘other’ in female/male relations. As for ecofeminism, she believes that by speaking for the original ‘others’, it seeks to understand the interconnected roots of all domination, and ways to resist the change.   Ã‚  Ã‚  Ã‚  Ã‚  Historically, people were more connected with the earth years ago, mainly because of the fact that many of these people were involved with the earth in some way in their daily lives, through being peasants and living a ordinary existence. But now the earth has become more mechanized and industrialized. Before that, the earth, the giver and supporter of life, was viewed as female, and symbolized by woman, as was the image of disorder, with her storms, droughts, and other natural disasters.   Ã‚  Ã‚  Ã‚  Ã‚  Judith Plant states that because of the view humans used to hold of the earth, they would in a way serve as constraints. ‘Mother Earth’ was seen to be alive and sensitive, and no one would consider destroying her in any way. A good example of this strong belief and view towards the earth could be seen in miners. In order to not prevent one of these rules, or in other words to not act ‘†improperly† towards ‘Mother Earth’ rituals were carried out. Miners would give offerings to the gods of the soil and the subterranean world, perform ceremonial sacrifices, and observe sexual abstinence and fasting before violating what was considered to be the sacred earth.   Ã‚  Ã‚  Ã‚  Ã‚  The change that resulted from the growth in the mechanized and industrialized world was very different. Unlike the visions of the earth before, the new images were of controlling and dominating or having power of nature. Eco-feminism :: essays research papers â€Å"Women have long been associated with nature.†   Ã‚  Ã‚  Ã‚  Ã‚  In the following essay Judith Plant sets out the main principles (in regards to ecofeminism): the closeness of women to nature; the belief that the domination of women and the destruction of nature have the same root cause; patriarchy; and the need to re-establish for nature the organic metaphor over the machine metaphor.   Ã‚  Ã‚  Ã‚  Ã‚  Judith Plant believes that women have long been associated with nature and that historically, women have had no real power in the outside world, no place in decision-making. Other things such as the intellectual life, the work of the mind, have traditionally not been accessible to women for many reasons. Some of these reasons have included society’s mentality. According to Judith, today, ecology speaks for the earth, and feminism speaks for the ‘other’ in female/male relations. As for ecofeminism, she believes that by speaking for the original ‘others’, it seeks to understand the interconnected roots of all domination, and ways to resist the change.   Ã‚  Ã‚  Ã‚  Ã‚  Historically, people were more connected with the earth years ago, mainly because of the fact that many of these people were involved with the earth in some way in their daily lives, through being peasants and living a ordinary existence. But now the earth has become more mechanized and industrialized. Before that, the earth, the giver and supporter of life, was viewed as female, and symbolized by woman, as was the image of disorder, with her storms, droughts, and other natural disasters.   Ã‚  Ã‚  Ã‚  Ã‚  Judith Plant states that because of the view humans used to hold of the earth, they would in a way serve as constraints. ‘Mother Earth’ was seen to be alive and sensitive, and no one would consider destroying her in any way. A good example of this strong belief and view towards the earth could be seen in miners. In order to not prevent one of these rules, or in other words to not act ‘†improperly† towards ‘Mother Earth’ rituals were carried out. Miners would give offerings to the gods of the soil and the subterranean world, perform ceremonial sacrifices, and observe sexual abstinence and fasting before violating what was considered to be the sacred earth.   Ã‚  Ã‚  Ã‚  Ã‚  The change that resulted from the growth in the mechanized and industrialized world was very different. Unlike the visions of the earth before, the new images were of controlling and dominating or having power of nature.

Educational Goals and Philosophy :: Teaching Education Careers Essays

Educational Goals and Philosophy How do I feel about teaching? I feel that the most important career an individual could choose would be education. Teachers play an important role in the lives of young children. They help shape and mold the world's future citizen that will run companies, be politicians, doctors, lawyers, teachers, electricians, construction workers, or whatever they desire. I feel that the most important role of a teacher is to provide children with the best possible education that is available. Teachers need to help young children learn and work up to their potential to be a productive, responsible citizen in society today. There are many strategies to use when providing the students with an appropriate education that meets all the individual's needs. I believe that the Greek philosophers Socrates, Plato, and Aristotle all played an important role in shaping the educational system. I basically agree with Socrates philosophy because he promoted intellectual insights in his students. The Socratic method was a challenge in Socrates time as it is today because people don't like change. They are hesitant when it comes to new approaches or strategies to teach the curriculum. Many educators still tend to use the conventional ideas and traditions to teach subject matter as opposed to keeping up with the current trends and technologies today. I also agree with parts of Plato and Aristotle's philosophies. I feel that a combination of the three would benefit any teacher. Progressivism is respect for individuality. My hope is to allow for this in my classroom. As I enter into the educational field and acquire more knowledge, I began to realize how different individual's needs are and how different methods have to be used to get across concepts being taught. Howard Gardner identified eight kinds of intelligences. The quality of a student's performance depends greatly on how they learn. I hope to meet all my student's needs by incorporating a wide variety of techniques in my lesson plans. I will use cooperative learning groups, peer tutoring, teach - reteach methods, hands - on activities, and the use of technology. I will be open - minded to any suggestions or any new approaches that may arise.

Mgt Syllabus

What about unethical but moral? Which is more important to an organization, to be ethical or moral? Why? What are ethics? How are personal ethics different than business ethics? Based on your work experience, describe an ethical issue that you faced. What were the ethical implications surrounding that issue, if any? How was the issue resolved or how should it have been resolved? Does your organization have a written code of conduct? If so, how effective is this cook AT conduct:' 10 want extent ay you tank Tanat a cook AT conduct can Nell to define the ethical values of an organization?How might a code of conduct policy reflect the personal ethics of the employees? What can a business do to reduce the likelihood of making unethical decisions ND creating more ethical problems? Think of an example of unethical behavior you have observed in a business setting. Was this behavior a result of an unethical person or an unethical organization? Explain your answer. Week Two Organizational Valu es ; Read Chi. 14 of Business ethics. ; Read Chi. 8-10, up. 115-118, up. 138-142 of Managing business ethics. 2. Discussion Questions What is the relationship between organizational values and organizational culture?Does organizational culture influence organizational values more than organizational values influence organizational culture? Explain your answer. How do organizational values of your organization influence its conduct? How do your organization's values influence you? How might a small business owner, whose business has grown from an owner and operator to employing 12 people over several years, create the organizational culture and organizational values of the business? Consider that the same business has grown to employ 100 or more people over several more years.How might the approach to organizational culture and values change depending on the size of the organization? What is the relationship between organizational values and personal values? Which of your personal va lues are embodied in your organization? How do employees' personal values influence the conduct of your organization? What issues might arise if employees' personal values are significantly different from their employer's organizational values? want Is winless-Doodling:' near want classmates malign an employee Low ten whistle on his or her employer?If the company's top executive asked you to create a code of ethics policy for the company, what would you include? What approach would you use? Why would you select that approach? Provide at least two examples of items you would include in your code of ethics and describe why they are important to your company's code. Think of a moral or ethical dilemma you experienced recently at work. What steps did you take to resolve the issue? In retrospect, how might you have handled the situation differently? How might this process be different if you were acting on behalf of the organization?How might you have handled the situation differently if you were the CEO? Imagine you are a division manager at a large pharmaceuticals company. You directly supervise 50 average and above average performing employees. Many employees on your team have been with the company for several years. Some recently hired employees, mostly women and minority groups, were hired to remedy the lack of diversity in the workplace. Recent financial difficulties within the company quire each division manager to reduce their workforce by 15%.Describe the process you would use to make this decision. How do you ethically Justify your decision? Do you think that you share the same ethical perspective as people who work with you? Explain your answer. Why is it important, or not, to share ethical perspectives in the workplace? What are the ethical standards for where you work? To what extent do you think that ethical perspectives may change over time? What factors might influence these changes? What is your experience working with or working for someone you fe lt had a much efferent ethical perspective than your own?How did you know when the two of you were approaching the same ethical dilemmas from different ethical perspectives? What was the outcome? How did your decisions or outcomes compare? Week Four Ethical and Legal Issues in Business course Agelessness ; Read Chi. 10 of Business ethics. ; Review Chi. 3, 8, & 10 of Managing business ethics. 2. Individual Assignment: Ethics Game Simulation Resource: Ethics Game Simulation Complete the Ethics Game Simulation. Write a 700- to 1,050- word reflective Journal in which you answer the following questions: What were the ethical issues presented in the simulation? What decision-making steps did you take to ethically address these issues? ;What ethical perspectives, or lenses, did you use to make your decisions in the simulation? ;How did these ethical perspectives, or lenses, influence your management decisions? ; How might concepts from this simulation relate to your workplace? Do you think human resources (HRS) polices should govern ethical and legal issues? Why or why not? How might HRS policies govern unethical or unlawful behavior? Do we need laws that enforce ethical codes? How might a situation in business be legal but unethical?How might a situation be ethical but illegal? Share an example from your own experience of HRS policies that address or encourage ethical practices. What is your definition of a stakeholder? Which of the different stakeholder groups' interests are the most important, and why? What ethical responsibilities does an organization have to different stakeholder groups? How might ignoring the needs of one stakeholder in favor of another stakeholder affect the organization? Provide an example. Why might a business want to appeal more directly to a secondary stakeholder roof than the primary stakeholders?What advantages might there be in doing this? Why might a business want to appeal more directly to a group that is not a stakeholder group? In w hat types of situations might this make sense? What is the difference between a stakeholder group and a special interest group? Name three examples of business or organizations in which you are a stakeholder. What makes you a stakeholder to these organizations? How are your views important to these organizations? Are your views aligned with the legal and ethical considerations of the organization? Explain your answer.Describe a time when another stakeholder group's views were in direct opposition of your views or the organization's flews. want napped Week Five Cross-cultural Ethics and Social Responsibility Analyze ethically and socially responsible business practices across cultures. ; Read Chi. 18 & 21 of Business ethics. ; Read Chi. 1 1 of Managing business ethics. 2. Individual Assignment: Final Examination Resources: Business ethics and Managing business ethics Click the link to the Final Examination on your student website available from the end of Week Four through the end of Week Five.Complete the Final Examination. You are allowed one attempt to complete the exam, which is timed and must be completed in 3 hours. Results are auto graded and sent to your instructor. Note. Final Examination questions are adapted from Business ethics and Managing business ethics. 3. Learning Team Assignment: Ethical Organization Profile Write a 1,050- to 1,750-word paper in which your Learning Team explains a fictitious organization's ethics programs and overall ethical environment. Create a fictitious organization. Describe the type of business, locations, size, and products or services offered. Write a value statement which includes: Overall ethics of the organization Socially responsible business practices Write a basic code of conduct. Select three of the following to include: ; practices ; Workplace discipline Termination of employment Diversity Harassment ; Family and personal issues Hiring Imagine your organization NAS cellar to Deign operations In another country. Identify the country and answer the following questions: What legal and ethical issues might your organization face with operations in that country? ; What stakeholder groups relevant to your organization would be affected by expanding operations into this new country? ; How might those groups influence he legal and ethical decisions your organization might make while expanding its operations? ; How might the legal and ethical issues faced in this country influence your organization's value statement and code of conduct? 4.Discussion Questions What must an organization consider from an ethical and socially responsible perspective before deciding to expand operations in other countries? How might an organization be considered ethical and socially responsible in its home country but not in the new country where they expanded operations? How might an organization balance varying views of ethical standards across cultures? Provide an example of a business currently addressing this issue and discuss any personal experience you may have with these issues. How might ethical and social responsibility issues, such as community service or environmentally responsible practices, affect an organization's operations in different regions of the US? What must an organization consider when expanding operations to Omaha, Nebraska; Santa Monica, California; Montgomery, Alabama; and Detroit, Michigan? Select two from the list to discuss in your response. Should a company vary its ethical and socially responsible business practices in different regions, even f laws which regulate the company's operations remain consistent across regions?Why or why not? What positive and negative outcomes might result from the choice the company makes about its ethical and socially responsible business practices in different regions? ; Imagine you are the marketing manager for a product you use daily, like gourmet coffees or paper towels, and you are selected to introduce the product to a new inter national market. What ethical or social responsibility issues, such as sustainability and fair trade, might you face when introducing the product to that raked? How might you overcome these issues?Name the product and the international market in your response. If your company plans to expand operations in a country known for human rights violations and sweatshop labor practices, what might you do to assure the media that the organization is committed to fair wages and running an honest, ethical factory? Would you consider choosing to open the factory elsewhere to prevent the media attaching the company's name to other companies that have abused and exploited ten workers Tort canapà © largo:' winy would you make tens console?

Input/Output Organization

INPUT/OUTPUT ORGANIZATION †¢ Accessing I/O Devices †¢ I/O interface †¢ Input/output mechanism Memory-mapped I/O y pp / Programmed I/O Interrupts Direct Memory Access †¢ Buses Synchronous Bus Asynchronous Bus I/O in CO and O/S †¢ †¢ †¢ Programmed I/O Interrupts DMA (Direct memory Access) A bus is a shared communication link, which uses one , set of wires to connect multiple subsystems. The two major advantages of the bus organization are versatility and low cost. Accessing I/O Devices Most modern computers use single bus arrangement for connecting I/O devices to CPU & Memory †¢ The bus enables all the devices connected to it to exchange information †¢ Bus consists of 3 set of lines : Address, Data, Control †¢ Processor places a particular address (unique for an I/O Dev. ) on address lines †¢ Device which recognizes this address responds to the commands issued on the Control lines †¢ Processor requests for either Read / Write †¢ The data will be placed on Data lines Hardware to connect I/O devices to b t bus Interface Circuit – Address Decoder – Control Circuits – Data registers – Status registers †¢ The Registers in I/O Interface – buffer and control †¢ Flags in Status Registers like SIN, SOUT Registers, SIN †¢ Data Registers, like Data-IN, Data-OUT I/O interface for an input device Memory Address Processor Data Control Address Add Decoders Control C t l circuits Data d t t D t and status registers I/O /O Interface Input device (s) p ( ) Input Output mechanism h i †¢ Memory mapped I/O †¢ Programmed I/O †¢ Interrupts †¢ DMA (Direct memory Access)A bus generally contains a set of control lines and a set of data lines. The control lines are used to signal requests and acknowledgments, and to indicate what type of information is on the data lines. The control lines are used to indicate what the bus contains and to implement the bus p rotocol. The data lines of the bus carry information between the source and the destination. This information may consist of data, complex commands, or addresses. Buses are traditionally classified as processor-memory di i ll l ifi d buses or I/O buses or special purposed buses (Graphics, etc. ).Processor memory buses are short, generally high speed, and matched to the memory system so as to maximize memoryprocessor bandwidth. I/O b buses, b contrast, can be lengthy, can have many by t t b l th h types of devices connected to them, and often have a wide range in the data bandwidth of the devices connected to them. I/O buses do not typically interface directly to the memory but use either a processor-memory or a backplane bus to connect to memory. The major disadvantage of a bus is that it creates a communication bottleneck possibly limiting the maximum I/O bottleneck, throughput.When I/O must pass through a single bus, the bus bandwidth of that bus limits the maximum I/O throughput. Reason why b R h bus d i design is so difficult : i diffi lt – the maximum bus speed is largely limited by physical factors: the length of the bus and the number of devices. These physical limits prevent us from running the bus arbitrarily fast. – In addition, the need to support a range of devices with widely varying latencies and data transfer rates also makes bus design challenging. – it becomes difficult to run many parallel wires at high speed due to clock skew and reflection reflection.The two basic schemes for communication on the bus are synchronous and asynchronous. If a bus is synchronous (e. g. Processor-memory), it includes a clock in the control lines and a fixed protocol for communicating that is relative to the clock. g This type of protocol can be implemented easily in a small finite state machine. Because the protocol is predetermined and involves little logic, the bus can run very fast and the interface logic will be small. Synchronous buses h ave two major disadvantages: – First, every device on the bus must run at the same clock rate. Second, because of clock skew problems, synchronous buses cannot be long if they are fast. An A asynchronous b h bus i not clocked. It can accommodate a is t l k d d t wide variety of devices, and the bus can be lengthened without worrying about clock skew or synchronization problems. To coordinate the transmission of data between sender and receiver, an asynchronous bus uses a handshaking protocol. Three special control lines required for hand-shaking: ReadReq: Used to indicate a read request for memory. The address is put on the data lines at the same time.DataRdy: Used t i di t th t th d t D t Rd U d to indicate that the data word is now ready on the di d th data lines; asserted by: Output/Memory and Input/I_O Device. Ack: Used to acknowledge the ReadReq or the DataRdy signal of the other party. I/O Dev. Memory Steps after the device signals a request by raising ReadReq and putti ng the address on the Data lines: 1. When memory sees the ReadReq line, it reads the address from the data bus and raises Ack to indicate it has been seen. 2. As the Ack line is high – I/O releases the ReadReq and data lines. g / q 3.Memory sees that ReadReq is low and drops the Ack line to acknowledge the ReadReq signal (Mem. Reading in progress now). 4. This step starts when the memory has the data ready. It places the data from the read request on the data lines and raises DataRdy. 5. The I/O device sees DataRdy, reads the data from the bus, and signals that it has the data by raising Ack. 6. On the Ack signal, M/M drops DataRdy, and releases the data lines. 7. Finally, the I/O device, seeing DataRdy go low, drops the Ack line, which indicates that the transmission is completed. Memory mapped I/O I/O devices and the memory share the same address space the space, arrangement is called Memory-mapped I/O. In Memory-mapped I/O portions of address space are assigned to I/O devi ces and reads and writes to those addresses are interpreted as commands to the I/O device. †¢ â€Å"DATAIN† is the address of the input buffer associated with the keyboard. – Move DATAIN, R0 reads the data from DATAIN and stores them into processor register R0; – Move R0, DATAOUT sends the contents of register R0 to location DATAOUT g Option of special I/O address space or incorporate as a part of memory address space (address bus is same always).When the processor places the address and data on the memory bus, the memory system ignores the operation because the address indicates a portion of the memory space used for I/O. The device controller, however, sees the operation, records the data, and transmits it to the device as a command. User programs are p p g prevented from issuing I/O g / operations directly because the OS does not provide access to the address space assigned to the I/O devices and thus the addresses are protected by the address translatio n. Memory mapped I/O can also be used to transmit data by writing or reading to select addresses.The device uses the address to determine the type of command, and the data may be provided by a write or obtained by a read. A program request usually requires several separate I/O operations. Furthermore, the processor may have to interrogate the status of the device between individual commands to determine whether the command completed successfully. DATAIN DATAOUT STATUS CONTROL 7 6 5 4 DIRQ KIRQ DEN KEN SOUT SIN 3 2 1 0 I/O operation involving keyboard and display devices Registers: DATAIN, DATAOUT, STATUS, CONTROL Flags: SIN, SOUT – Provides status information for keyboard nd display unit KIRQ, DIRQ – Keyboard, Display Interrupt request bits DEN, KEN –Keyboard, Display Enable bits Programmed I/O †¢ CPU has direct control over I/O – S Sensing status i t t – Read/write commands – Transferring data †¢ CPU waits for I/O module to comple te operation †¢ Wastes CPU time In this case, use dedicated I/O instructions in the processor. These I/O instructions can specify both the device number and the command word (or the location of the command word in memory). The processor communicates the device address via a set of wires normally included as part of the I/O bus.The actual command can be transmitted over the data lines in the bus. bus (example – Intel IA-32) IA-32). By making the I/O instructions illegal to execute when not in kernel or supervisor mode user programs can be mode, prevented from accessing the devices directly. The process of periodically checking status bits to see if it is time for the next I/O operation, is called polling. Polling is the simplest way for an I/O device to communicate with the processor processor. The I/O device simply puts the information in a Status register, register and the processor must come and get the information.The processor is totally in control and does all the w ork. A ISA program to read one line from the keyboard, store it in memory buffer and echo it back to the display buffer, The disadvantage of polling is that it can waste a lot of processor time because processors are so much faster than I/O devices devices. The processor may read the Status register many times, only to find that the device has not yet completed a comparatively slow I/O operation, or that the mouse has not budged since the last time it was polled.When the device completes an operation, we must still read the status to determine whether it (I/O) was successful. Overhead in a polling interface lead to the invention of interrupts to notify the processor when an I/O device requires attention from the processor. Interrupt-driven I/O, Interrupt driven I/O employs I/O interrupts to indicate to the processor that an I/O device needs attention. When a device wants to notify the processor that it has completed some operation or needs attention, it causes the processor to be in terrupted.Interrupts I/O INTERRUPT Processor †¢ When I/O Device is ready, it sends the INTERRUPT signal to processor via a dedicated controller line †¢ Using interrupt we are ideally eliminating WAIT period †¢ In response to the interrupt, the processor executes the Interrupt Service Routine (ISR) †¢ All the registers flags program counter values are saved registers, flags, by the processor before running ISR †¢ The time required to save status & restore contribute to execution overhead ? â€Å"Interrupt Latency† p y nterrupt-acknowledge signal – I/O device interface p y accomplishes this by execution of an instruction in the interrupt-service routine (ISR) that accesses a status or data register in the device interface; implicitly informs the device that its interrupt request has been recognized. IRQ signal is then removed by device. ISR is a sub-routine – may belong to a different user than the one being executed and then halted. The c ondition code flags and the contents of any registers used by both the interrupted program and the interrupt-service interrupt service routine are saved and restored restored.The concept of interrupts is used in operating systems and i many control applications, where processing of d in l li i h i f certain routines must be accurately timed relative to external events (e. g. real-time processing). Interrupt Hardware p Pull up Pull-up resister INTR = INTR1 +†¦.. +INTR n INTR An equivalent circuit for an open drain bus used to implement a open-drain common interrupt-request line Interrupt Hardware Supply pp y R INTR Processor Pull-up resister INTR 1 INTR 2 INTR 3 INTR = INTR1 +†¦.. +INTR n GND INTR Enabling and Disabling Interrupts Device activates interrupt signal line and waits with this signal activated until processors attends †¢ The interrupt signal line is active during execution of ISR and till the device caused interrupt is serviced †¢ Necessary to ensure t hat the active signal does not lead to successive interruptions (level-triggered input) causing (level triggered the system to fall in infinite loop. †¢ What if the same d i h h device i interrupts again, within an ISR ? i i hi †¢ Three methods of Controlling Interrupts (single device) – Ignoring interrupt – Disabling interrupts – Special Interrupt request line Ignoring Interrupts – Processor hardware ignores the interrupt request line until the execution of the first instruction of the ISR completed – Using an interrupt disable instruction after the first instruction of the ISR – no further interrupts – A return from interrupt instruction is completed before further interruptions can occur †¢ Disabling Interrupts – Processor automatically disables interrupts before starting the execution of the ISR – The processor saves the contents of PC and PS (status register) before performing interrupt disabling. The interrupt-enable is set to 0 – no further interrupts allowed – When return from interrupt instruction is executed the contents of the PS are restored from the stack, and the interrupt enable is set to 1 †¢ Special Interrupt line p p – Special interrupt request line for which the interrupt handling circuit responds only t th l di h dli i it d l to the leading edge of d f the signal – Edge –triggered g gg – Processor receives only one request regardless of how long the line is activated – N separate i t No t interrupt di bli t disabling i t instructions tiThe sequence of events involved in handling an interrupt request from a single device. Assuming that interrupts are enabled, the following is a typical scenario: 1. 1 The device raises an interrupt request request. 2. The processor interrupts the program currently being executed. t d 3. Interrupts are disabled by changing the control bits in the PS (except in the case of edge-tri ggered interrupts) interrupts). 4. The device is informed that its request has been recognized, and in response, it deactivates the interrupti d di d ti t th i t t request signal. . The action requested by the interrupt is performed by the interrupt-service routine. 6. Interrupts are enabled and execution of the interrupted program is resumed. Handling Multiple Devices †¢ Multiple devices can initiate interrupts p p †¢ They uses the common interrupt request line y p q †¢ Techniques are q – Polling – Vectored Interrupts p – Interrupt Nesting – Daisy Chaining y g Polling Scheme †¢ The IRQ (interrupt request) bit in the status register is set when a device is requesting an interrupt. The Interrupt service routine polls the I/O devices connected to the bus. †¢ The first device encountered with the IRQ bit set is serviced and the subroutine is invoked. †¢ Easy to implement, but too much time spent on checking the IRQ bits of all d evices, though some devices may not be requesting service. Vectored Interrupts †¢ Device requesting an interrupt identifies itself directly to the processor †¢ The device sends a special code to the processor over the bus. The code contains the – identification of the device device, – starting address for the ISR, – address of the branch to the ISR †¢ PC finds the ISR address from the code. †¢ To add flexibility for multiple devices – corresponding ISR is executed by the processor using a branch address to the appropriate routine – device specified Interrupt Vector. An interrupt vector is the memory address of an interrupt handler, or an index into an array called an interrupt vector table or dispatch table – a table of interrupt vectors (pointers to routines that handle interrupts).Interrupt vector tables contain the memory addresses of interrupt handlers. When an interrupt is generated, the processor saves its execution state via a context switch, and begins execution of the interrupt handler at the interrupt b i ti f th i t t h dl t th i t t vector. The Interrupt Descriptor Table ( p p (IDT) is specific to the ) p I386 architecture. It tells where the Interrupt Service Routines (ISR) are located. Each interrupt number is reserved for a specific purpose. For example, 16 of the vectors are reserved for the 16 IRQ lines.Q On PCs, the interrupt vector table (IVT or IDT) consists of 256 4-byte pointers – the first 32 (0-31 or 00-1F) of which are reserved f for processor exceptions; the rest f for hardware interrupts, software interrupts. This resides in the first 1 K of addressable memory. Interrupt Nesting †¢ Pre-Emption of low priority Interrupt by another high Pre Emption priority interrupt is known as Interrupt nesting. †¢ Di bli Disabling I t Interrupts d i t during th execution of th ISR the ti f the may not favor devices which need immediate attention. Need a priority of IRQ de vices and accepting IRQ from a high priority device. †¢ The priority level of the processor can be changed y y dynamically. †¢ The privileged instruction write in the PS (processor status word) that encodes the processors priority word), priority. Interrupt Nesting (contd. ) Pro ocessor INTR1 Device 1 INTA 1 Device 2 INTRp .. . Device p INTA p Priority arbitration circuit †¢ Organizing I/O devices in a prioritized structure. g g / p †¢ Each of the interrupt-request lines is assigned a different priority level level. †¢ The processor is interrupted only by a high priority device. Daisy Chaining †¢ †¢ †¢ †¢ The interrupt request line INTR is common to all the devices The interrupt acknowledgement line INTA is connected to devices in a DAISY CHAIN way INTA propagates serially through the devices Device that is electrically closest to the processor gets high hi h priority i i Low priority device may have a danger of STARVATION INTR P Processo r r Device D i 1 INTA Device D i 2 .. Device n D i Daisy Chaining with Priority Group †¢ †¢ Combining Daisy chaining and Interrupt nesting to form p priority group yg p Each group has different priority levels and within each group devices are connected in daisy chain wayINTR1 Proc cessor Device 1 Device 1 INTA 1 INTR p . . . . Device D i 1 INTA p Priority arbitration circuit Device D i 1 Arrangement of priority groups Direct Memory Access (DMA) †¢ For I/O transfer, Processor determines the status of I/O devices, by – – Polling Waiting for Interrupt signal †¢ Considerable overhead is incurred in above I/O transfer processing †¢ To transfer large blocks of data at high Speed, between EXTERNAL devices & Main Memory, DMA approach is often used †¢ DMA controller allows data transfer directly between I/O device d i and d Memory, M with i h minimal i l intervention i i of f processor. Direct Memory Access (DMA) †¢ DMA controller acts as a P rocessor, but it is controlled by CPU †¢ To initiate transfer of a block of words, the processor sends the following data to controller – The starting address of the memory block – The word count h d – Control to specify the mode of transfer such as read or write – A control to start the DMA transfer †¢ DMA controller performs the requested I/O operation and sends a interrupt to the processor upon completion 1 Status and Control Starting address Word count In ? ? ? IRQ 30 IE 1 R/W 0 Done DMA interface g g First register stores the starting address Second register stores Word count Third register contains status and control flags Bits and Flags R/W Done IRQ IE 1 READ Data transfer finishes Interrupt request Raise interrupt (enable) after Data Transfer 0 WRITE Processor Main memory Disk/DMA controller DMA controller Printer Keyboard Disk Disk Network Interface Use of DMA Controller in a computer system Memory accesses by the processor and DMA Cont roller are interwoven †¢ DMA devices have higher priority then processor over BUS control †¢ Cycle Stealing:- DMA Controller â€Å"steals† memory cycles from processor, though processor originates most memory access. †¢ Block or Burst mode:- The of data without interruption †¢ Conflicts in DMA: – Processor and DMA, – Two DMA controllers, try to use the Bus at the same time to access the main memory DMA controller may given exclusive access to the main memory to transfer a blockDMA and Interrupt Breakpoints During D i an I t Instruction Cycle ti C l Bus Arbitration †¢ Bus master: device that initiates data transfers on the bus. †¢ The next device can take control of the bus after the current master relinquishes control †¢ Bus Arbitration: process by which the next device to become master is selected †¢ Centralized and Distributed Arbitration BBSY P Processor r BR BG1 DMA controller 1 BG2 DMA controller 2 A simple arrangemen t for bus arbitration using a daisy chain BR (bus request ) line – open drain line – the signal on this line is a logical OR of the bus request from all the g q DMA devices – BG (bus grant) line – processor activates this line indicating (acknowledging) to all the DMA devices (connected in daisy chain fashion) that the BUS may be used when its free free. – BBSY (bus busy) line – open collector line – the current bus master i di b indicates d i devices that i i currently using h it is l i the bus by signaling this line BBSY Processor BR BG1 DMA controller 1 BG2DMA controller 2 Sequence of signals during data transfer of bus mastership †¢ Centralized Arbitration – Separate unit (bus arbitration circuitry) connected to the bus – Processor is normally the bus master, unless it grants bus mastership to DMA For the timing/control, in previous slide: DMA controller 2 requests and acquires bus mastership and later releases the bus. During its tenure as the bus master, it may perform one or more data transfer operations, depending on whether it is p , p g operating in the cycle stealing or block mode.After it releases the bus, the processor resumes bus mastership. †¢ Distributed Arbitration – All devices waiting to use the bus has to carry out the arbitration process – no central arbiter – Each device on the bus is assigned with a identification number 4-bit – One or more devices request the bus by asserting q y g the start-arbitration signal and place their identification number on the four open collector lines – ARB0 through ARB3 are the four open collector lines – One among the four is selected using the code on the lines and one with the highest ID numberA distributed arbitration scheme Assume that two devices, A and B, having ID numbers 5 and 6, respectively, are requesting the use of the bus. Device A transmits the pattern 0101, and device B transmit s the pattern 0110. p The code seen by both devices is 0111. Each device compares the pattern on the arbitration lines to its own ID, starting from the most significant bit. If it detects a difference at any bit position, it disables its drivers at that bit position and for all lower-order bits. It does so by placing a 0 at the input of these drivers drivers.In the case of our example, device A detects a difference on line ARB I. Hence, it disables its drivers on diff li I H i di bl i d i lines ARB 1 and ARBO. This causes the pattern on the arbitration lines to change to 0110, which means that B has won the contention. Universal Serial Bus (USB) The USB supports two speeds of operation called lowoperation, low speed (1. 5 megabits/s) and full-speed (12 megabits/s). The Th most recent revision of the bus specification (USB i i f h b ifi i 2. 0) introduced a third speed of operation, called high-speed (480 megabits/s).The USB has been designed to meet several key objectives: -P Provid e a simple, low-cost, and easy to use interconnection id i l l t d t i t ti system that overcomes the difficulties due to the limited number of I/O ports available on a computer – Accommodate a wide range of data transfer characteristics for I/O devices, including telephone and Internet connections / , g p – Enhance user convenience through a †plug-and-play† mode of operation USB Bandwidths: A low-speed rate of 1. 5 Mbit/s (~183 kB/s) is defined by USB 1. 0.It is intended primarily to save cost in lowbandwidth human interface devices (HID) such as keyboards, ( ) y , mice, and joysticks. The full-speed rate of 12 Mbit/s (~1. 43 MB/s) is the full speed ( 1. 43 basic USB data rate defined by USB 1. 1. All USB hubs support full-bandwidth. A high-speed (USB 2. 0) rate of 480 Mbit/s (~57 MB/s) was introduced in 2001. All hi-speed devices are capable of falling back to full bandwidth operation if necessary; they are full-bandwidth backward compatible. Connectors a re identical. SuperSpeed ( d (USB 3. 0) rate produces upto 4800 Mbit/s ) d bi / (~572 MB/s or 5 Gbps)Each node of the tree has a device called a hub, which acts as an intermediate control point between the host and the I/0 devices devices. At the root of the tree, a root hub connects the entire tree to the host computer. The leaves of the tree are the I/0 p / devices being served. The tree structure enables many devices to be connected while using only simple point-topoint serial links. Each hub has a number of ports where devices may be connected, including other hubs. In normal operation, a hub g copies a message that it receives from its upstream connection to all its downstream ports.As A a result, a message sent b the host computer is lt t by th h t t i broadcast to all I/O devices, but only the addressed device will respond to that message. A message from an I/O device is sent only upstream towards the root of the tree and is not seen by other devices. Hence, th USB enables th h t t communicate with the I/O H the bl the host to i t ith th devices, but it does not enable these devices to communicate with each other. The USB operates strictly on the basis of polling. A device may send a message only in response to a poll message from the host host.Hence, upstream messages do not encounter conflicts or interfere with each other, as no two devices can send other messages at the same time. This restriction allows hubs to be simple, low-cost devices. USB protocol requires that a message transmitted on a highspeed link is always transmitted p y at high speed, even when the ultimate receiver is a low-speed device. device Hence, a message intended for device D is sent at high speed from the root hub to hub A, then A forwarded at low speed to device D. The latter transfer will take a long time, during which highl ti d i hi h hi h speed traffic to other nodes is allowed to continue.Each device on the USB, whether it is a hub or an I/O device, is assigned a 7-bit ad dress. This address is local to the USB tree and is not related in any way to the addresses used on the processor bus. A hub may have any number of devices or other hubs connected to it, and addresses are assigned arbitrarily. When a device is first connected to a hub, or when it is powered on, it has the address 0. The hardware of the hub to which this device is connected is capable of detecting that the device has been connected, and it records this f d hi fact as part of i own status i f f its information. Periodically, the host polls each hub to collect status information and learn about new devices that may have been added or disconnected. When the host is informed that a new device has been connected, connected it uses a sequence of commands to send a reset signal on the corresponding hub port, read information from the device about its capabilities, send configuration information to the device, and assign the device a unique USB address. O d i d i th d i i dd Once this thi se quence is completed the device begins normal operation and responds only to the new address. Read about USB protocols Isochronous traffic on USB and USB FRAME