How Do We Create A Society - 900 Words

Humans are creatures of power. They crave it, and they put it above all else. Humans are driven by their passions and not by reason or religion. The biggest passion humans crave is self-love. For this reason, all men are out for each other. The only thing they want is power and they will stop at nothing to attain that goal. In this quote, Cato explains what a man in power will do â€Å"But a tyrant shall, out of a wanton personal passion, carry fire and sword through a whole continent, and deliver up a hundred thousand of his fellow creatures to the slaughter in one day, without any remorse or further notice, than that they died for his glory†. (Cato 25). As we have learned, men are restless at their attempts to acquire power, but the real question is, how do we contain these urges? Cato has attempted to show us that in order to control men’s urges we need to create a society whose main goal is to prevent self-destruction of mankind. In order for this to occur, we need to create laws and institutions that serve to stop the greed of men. In this quote, Cato is explaining why it’s necessary to give the power to those who truly deserve it â€Å"It is therefore owing more to the necessities of men, than to their inclinations, that they have put themselves under the restraint of laws, and appointed certain persons, called magistrates, to execute them† (Cato 33). Men are controlled by their passions and without a proper government to control these urges we will be left with bloodshed.Show MoreRelatedCollin Labranche. May 9Th, 2017. Barosky. English 102.1227 Words   |  5 PagesMay 9th, 2017 Barosky English 102 Home The novel Gulliver s Travels by Jonathan Swift displays the vast difference of the Houyhnhnms society in comparison to ours. Harrison’s essay describes the way our society perceives home much differently than the way Houyhnhnms do. In modern day, and more specifically in the 18th century the family system that we associate with views home as a place for love, family, and support. In comparison to the Houyhnhnms, they use the home as more a community areaRead MorePros And Cons Of Artificial Intelligence1439 Words   |  6 Pagesas a society, we must first look back at all the hardships faced throughout the years. We must look at the world leaders who were able to convince entire countries to eliminate millions of people different than themselves. We must understand the groups of extremists spreading terror and fear across the globe, and we must control people in power abusing their positions to benefit themselves and their agendas. Instead of ignoring these human mistakes, we must break them down and figure out how theyRead MoreA Utopian world is impossible to create because nature would not allow it. Shakespeare’s play shows700 Words   |  3 PagesA Utopian world is impossible to create because nature would not allow it. Shakespeare’s play shows that no matter how much language players and technology changes human nature overall is misinterpreted. In order to have a perfect world, we need conflicts to occur because imperfection is key to perfection. A Utopian society only revolves in a persons mind. A person might think of a Utopian Society to escape their situation but they do not look at the disadvantages, let us take killing, for exampleRead More Matrix the Movie and The Lathe of Heaven Essay1652 Words   |  7 Pagesmovies and novels societies that are portrayed in our society as well. Also, each proves LeGuins theory on science fiction. The Lathe of Heaven and The Matrix have many similarities. Both utilize the number three by providing main characters in sets of three. Also, The Matrix brings an even more blatant example of this by naming one of the main characters Trinity. In addition, they both portray our world as something that is artificial; made up by others who do not have the bestRead MoreEducation Is A Better World1032 Words   |  5 Pagesapply this knowledge to the real world. Through doing this within the classroom, educations larger goal is create a better world. In order to reflect on how education creates a better world, I will explore the goals of education in Alberta, life long learning, and the impacts of education on society. Education is a unique field in that it is always changing. Education fosters the growth of society by constantly adapting and progressing in order to prepare model citizens to play a role in bettering theRead MoreAnalysis Of Aldous Huxley s Brave New World1287 Words   |  6 PagesThe constant development of society is faulted with the advancement of technology. Aldous Huxley’s Brave New World presents a controlled society which creates a faulty idea of perfection to be obtained. The theme of technology being used to control society is faulted. The attainment of perfection is faulted through symbolism with the assembly line producing children, the taking of the drug soma, and the changing of one s individual appearance to have all people look alike. The assembly of childrenRead MoreAnalysis Of Mary Shelley s Frankenstein Essay1267 Words   |  6 Pagesaccurate to the original novel. The scenes that Branagh changes have a better meaning in today’s society. In this classic gothic novel, Shelley, writes about many touchy and important topics like fear, abandonment, acceptance, death, impulse, rejection, life, and many more not listed that are prevalent today; each scene discussed has a theme that reaches outside the novel and the time period to create another relevant message that is still evident today. With the creation scene of the monster muchRead MoreAmerican Society : Film Review1584 Words   |  7 PagesAmerican Society in Films American society is not accurately reflected in films. In 1878 American society was introduced to the world of film. Films were a remarkable new innovation that showed Americas advances in technology. Not only was film new and exciting but, it also changed how people experienced emotions. Films have become a huge source of entertainment today but, films do not always accurately reflect American society. Furthermore, teens are not as rebellious as portrayed in films. InRead MoreFamily Is A Word With Diverse Meaning1539 Words   |  7 PagesFamily is considered a basic cell of society. All social and cultural practices find their connection with a notion of family, either supporting or distorting it†. This definition relate more so to how Fedorak explains family on pg 106. Family is a big part of what defines how close knit a community is, jutted based on how different the definitions are we can how much closer African families are then North American families . In Canada, our society is changing. We are transitioning to a new style ofRead More`` The Handmaid s Tale `` By Margaret Atwood And Gary Ross1542 Words   |  7 Pagescontext in which they were composed. The conventional themes through which they do this are uniformity, technology and removal from present time as well as how these concepts are manipulated to create new meanings. In Atwood’s 1986 novel ‘The Handmaid’s Tale’ the theme of uniformity, conventional to dystopian literature arises from the consideration of America’s fundamentalist Christian society. The convention of a ruling society or class is manipulated to be presented as a fundamentalist theocracy. The

Sexism in the Catholic Church free essay sample

Since the beginning of history, sexism has always been a prominent barrier between sexes. The notion that women are not on the same level as men has always been in existence. Even in the church there are accusations of sexism. We see it during the book of exodus this belief stems from the creation of Eve, through a rib of Adam. From scripture, Eves roll was to be considered as a servant and a temptress, the sole reason why Adam ate the apple. Consequently Eve is blamed as being the reason mankind is not living in a paradise. This is why I chose to study sexism, it has always been a topic within the church that I have not fully understood. Sexism is defined as the discrimination or hatred against people based on their gender rather then their individual merits. We see examples of this in modern day such as; a girl cannot play on a football team because of her gender, and likewise a male cannot be on a cheerleading squad because of his gender. There are multiple organizations and associations that make this more aware to the and help bring recognition to these issues. However sexism has been around since the ancient years and it has roots. Sexism in its general usage is directed against females. In ancient Greece, going back over twenty-five hundred years ago, women were born as property that belong to their fathers. This ownership was given to the husband as the woman became older. Women were also judged to be not worthy of male accompaniment, in older days women would bring dowries to their husbands. These dowries were used as payment for marriage. They would consist of things like gold and livestock. This is a legitimate example of how many sexist laws, beliefs or teaching would have been rooted from ancient and cultural pasts and still carry and alter our opinions today. The Church has been criticized many times on acts of sexism. The number one, main reason, that people accuse the church of sexism is the rule that women can not become priests. (Russell, 3) Or in that manner anything higher than a nun. People hear this and think well gee a guy can be a priest and a women can not this is a pure example of sexism. Dont we profess that God created men and women of equal worth and dignity? The Holy Scriptures state clearly in Galatians 3:28 that There is neither male nor female. In Christ Jesus you are one. ( Galatians 3:28) Catholic priests say that the call to be a priest is a gift and comes from God. How can mans call from God be real but a womens can not? (Hardon, 2028) However the Church addresses this with much confidence. The Catholic Church states that a priest must be male because a priest must represent Jesus, to stand in his place and since Jesus was male, so should the priest. â€Å"Barring women from being Catholic priests is not the result of sexism 2,000 years ago, its because women cannot fulfill a basic function of the priesthood, standing in the place of Jesus,†. ( Rogers, 1) Father Stephen Wang defends the Church by stating â€Å" This teaching is not at all a judgment on womens abilities or rights. It says something about the specific role of the priest in Catholic understanding which is to represent Jesus, to stand in his place† (Rogers, 2) Another key point brought up is that Jesus ordained the first priests, the apostles, they were all men, he must have intended for this. (Smith. 3) It is easy for people to over look the details and to see the broad side of things, assuming the church is being sexist towards females wishing to become priests. However to obtain the most authentic connection to god we can achieve the Catholic Church believes that only Males should be priests, to stand in his place. The Roman Catholic Church sees sexism as a social sin. There are many examples of the Church making statements about the importance of women in the church: Pope Benedict XVI stated â€Å"The history of Christianity would have had a very different development if it had not been for the generous support of many women who played an effective and precious role in spreading the Gospel. Their witness cannot be forgotten. † (Allen,1). Pope John Paul II also states â€Å"The Church desires to contribute to upholding the dignity, role and rights of women. Thank you, every woman, for the simple fact of being a woman! Through the insight which is so much a part of your womanhood you enrich the worlds understanding and help to make human relations more honest and authentic. (Howards, 3) The Catholic Church shows much importance for women. They state that each of the two sexes is an image of the power of God, with equal personal dignity though in different ways. A symbol of women of the Catholic Church is Mary. This symbol should speak for itself. Mary mother of Jesus Christ who we often pray to shows importance of women in the Catholic Church. Its easy to look at some of the Church’s policies and instantly assume that they are sexist in one way or another. However through deeper meaning we can see that the church is just trying to be as authentic and honest as possible. I believe that the Catholic Church is not at all sexist and are just trying to preserve their tradition and be authentic as possible. I don’t see the church bashing women claiming that they are not good enough to be a priest but rather they are just not fit for it, just as a man is not fit to give birth to a child. It was at first a little surprising that women have no chance what so ever of becoming a priest. However after deeper viewing I know understand the reasons behind it and completely agree with the Churches policy. What I found in my research I believe to be true, it came from many valid sources including the pope himself. My research definitely enhanced my faith. I know see how priest are meant to stand in place of Jesus and that only men are priest to keep the mass as authentic and honest as possible. There were not many other instances of the Church being accused of sexism to wright about, I wish I could have found more instances to study. However its good that the Church has not been accused of Sexism often. In Conclusion Sexism has been around for ages, it stems from ancient times and it is still seen in society today. The Catholic Church is often accused of sexism based of the policy that only men can be priests, however Jesus chose all men to be ordained as the first priests of his time, the apostles, and men are used as priest to be the closest resemblance to Jesus and to stand in his place during our sacred ceremonies. I conclude that the Church is not at all sexist and preach often about their importance of women, they are only trying to achieve the most pure authentic representation of Jesus as possible. They do this using a man.

Thenile Essay Example For Students

Thenile Essay Without the Nile, the great Egyptian back in the Ancient Times would have been nothing, except for an empire filled with sand. But the gods were with Egypt that time, and gave Egypt the only hope of surviving The Nile River. The Nile is the longest river on Earth. But now Egypt has started developing and changing, let alone mention that it is worldwide known. In Egypt, people have both adapted to their environment and changed their environment. One thing the Egyptians havent changed much is the Nile River. After they found out that farming could not be done in deserts, they soon found a use for the Nile River. They started farming there, realizing that there was fertile land by the river. Unfortunately, there was not enough land for more than 53,153,000 people, so they adapted to it, and started to use diesel pumps, to lift irrigation water from the Nile. Since they were too tired to cultivate land all day long, they took camels, buffaloes, goats, and cattle for granted, and used the m for cultivating land. Every year, they lay more pipes ; dig more ditches to reach water. A very important change the Egyptians have done is that they discovered that the Nile could also be a power source for hydroelectricity. Soon after, the Aswan High Dam was built up. The Egyptians also built the Suez Canal, the most important canal in the world; it helps ships sail to Asia from Europe in a fast way. Bibliography:Encarta We will write a custom essay on Thenile specifically for you for only $16.38 $13.9/page Order now

The Scarlet Letter Essays - English-language Films, Free Essays

The Scarlet Letter Essays - English-language Films, Free Essays The Scarlet Letter The Scarlet Letter, by Nathaniel Hawthorne, delivers a powerful novel invoked with symbolism. Centered on Hester, a woman branded with a scarlet A as a mark for adultery, much of the Scarlet Letters symbolism grows from the cruel, and shameful letter. The A symbolizes the walking emblem of shame. (Hawthorne 6). Throughout the novel, the brand of disgust evolves around the characters influenced by Hester, including her illegitimate child Pearl. Even Pearl is subject to the shame her mother has bore, and is also shunned from the strict Puritan society. The close of the novel reveals that the symbol has given Hester strength to redeem her sin, rather then brake her spirits. The adulterous mark is almost replaced by the community as able due to Hesters deeds to the community. Scarlet Letter also uses nature's flowers as a way to symbolize growth in the novel. The opening chapter describes a rosebush growing by the prison. It shows how even a beautiful flower like the rose can be judged as sacrificial, with its petals near the jail. This relates to Hester, as her beautiful character is judged by sin, not by actions. Later in the novel, Chillingworth, Hesters husband, expresses to let the black flower blossom as it may. (Hawthorne 14). This reoccurrence of the flower shows how Chillingworth accepts his tortuous soul. The flower's bloom is a direct symbol for the growth of character in Scarlet Letter. Clothing is a final source Hawthorne uses to symbolize. In chapter 7, Pearl is dressed in a red gown, with gold trim. The dress of Pearl is almost identical to the brand Hester must endure, with her scarlet brand. Chillington is dressed in black, which gives an insight into his sinister character, as revealed in chapter 14. Also, the use of bright color, like red, and gold expresses how different Hester and Pearl are viewed by the Puritan society, which mainly dresses in plain, emotionless colors. The brand of sin is reflected in all the aspects of Hesters life, which show how clothing in Scarlet Letter drastically reflects situation, and character. Hawthorne's Scarlet Letter gives a tremendous impression on the reader, filled with oppression, and historical opinion of the Puritans. Unfortunately, as the novel appears to mirror reality, situations in the storyline leave the reader skeptical about the actual ability to perform these actions. Hesters sudden removal of the scarlet brand bestowed upon her seems very unrealistic, considering it took seven years to remove it so quickly, and carefree. It almost makes the symbol of the scarlet letter obsolete at the end of the chapter 18, leaving insinuation that the letter did not have as much influence as formerly expressed. The Scarlet Letter also confuses the reader during chapters after 20. The final pages of the novel give a completely different perspective. Generally focused on the main characters, during chapter 21, and 22, the market gives a more broad insight into the community. While it makes for interesting reading, the sudden change of perspective leaves the reader strayed from the main characters, like Hester, and Pearl. The Scarlet Letter is a very intriguing novel, for anyone looking to find a tale of Puritan life, and the harsh reality of the times. Overall, the Scarlet Letter delivers an exciting, and interesting view for all readers.

FedEx Express Essay Example | Topics and Well Written Essays - 1000 words

FedEx Express - Essay Example FedEx started its business long back in 1997 as a logistics services company which specialization was import/ export division with the name FDX. But it started its full operation in 1998 after the acquisition of Caliber System Inc. After that it started ground services with express shipping. Caliber handled the small package ground service and RPS; Viking Freight handled the less than truck loads throughout the western United States, Roberts Express handled the shipping services, airfreight services between Caribbean and United States handled by Caribbean Transportation Services. For technology solutions it got help from Caliber Logistics and Caliber Technology. Later in 2000 FedEx bought Tower Group International which was a logistics services company working internationally and WorldTariff which was a tax and customs duty organization. And then merged those two organizations, and form FedEx Trade Network. (FedEx Express, 2013) The main line of business of the FedEx Express: Later i n 2004 FedEx Corp takes over Kinko’s Inc. and set up FedEx Kinko’s. After this merging FedEx not only became a logistics provider for organizations but it enhance its operation to the individual public. After that all the FedEx Kinko retail stores starts offering shipping exclusively but later in 2008 FedEx exclude Kinko’s name from its name and made it FedEx Office. During 2004, FedEx bought Parcel Direct and renamed it as FedEx SmartPost. FedEx Express is an airline service which only dealt with cargo. In terms of freight tons it is the largest airline of the world and in terms of size of the fleet the fourth largest airline of the world. Names of the countries in which the FedEx operates: FedEx Express served to 375 destinations every day to almost all the countries. As the largest express transportation company of the world it headquarters in Memphis International Airport except that in United States of America its national hub is in Indianapolis Internation al Airport. Other regional hubs in United States of America are Ted Stevens Anchorage International Airport, Oakland International Airport, Newark Liberty International Airport, Fort Worth Alliance Airport and Miami International Airport. Outside of United States of America other regional headquarters are like Paris-Charles de Gaulle Airport, Guangzhou Baiyun International Airport, Toronto Person International Airport and Cologne Bonn Airport. Another airport which was about to open for FedEx Express was Piedmont Triad International Airport. 4P's marketing mix concept by the FedEx: Competition: Competitors for FedEx are ARAMEX, BAX Global, Choice Logistics, DHL Express, Purolator Courier, TNT N.V., United Parcel Service etc. Other freight competitors for FedEx Express in international market are like DHL, UPS (United Postal Service) from United States. And from foreign countries like Deutsche Post, TNT N.V. Except them others are like freight forwards, and other passengers and cargo airlines. Many competitors of FedEx are government controlled or subsidized organizations. Because of that those organizations have better resources; costs of services are low, low profit margin and favors regarding government policies and rules-regulations. Target market: FedEx made a seven year contract in

The Amyloid Formation by Amyloid precursor protein and its role in Essay

The Amyloid Formation by Amyloid precursor protein and its role in Alzheimer's disease - Essay Example y have been identified so far, with each disease having a characteristic and distinct clinico-pathological profile and each disease associated with aggregation of a specific single protein or peptide that is dominant (Chitti and Dobson, 2008). One such classical disease in which there is disordered accumulation of protein is Alzheimers disease and the protein that is accumulated is amyloid. In this essay, the role of amyloid in the pathogenesis of Alzheimers disease will be discussed with reference to its production, deposition, alteration, regulation, processing and trafficking, through review of suitable literature. Alzheimers disease (AD) is a common degenerative disease of the brain that leads to dementia (Anderson, 2010). Infact, it is the most common cause of dementia and is incurable. The disease is an acquired condition in which there is impairment of cognition and behavior of the individual that is severe enough to disrupt normal occupational and social functioning of the individual. AD is a major public health problem associated with significant morbidity, impairment and economic consequences (Anderson, 2010). More often than not, the disease is mainly diagnosed after 65 years of age, although, an early-onset variety of AD does exists which presents much early. According to Brookmeyer et al (2007), 1 in 85 people in the world are likely to suffer from AD by 2050. The course of the disease is different for different individuals and thus is the prognosis. The most common early symptom, which is often ignored as an aging feature or stress consequence is the lack of ability to acquire new m emories. Other symptoms include changes in cognition and behavior of the individual like irritability, confusion, aggression, mood swings, breakdown in language, withdrawal and long term loss of memory. As the age advances, various functions of the body are gradually lost, terminating in death. AD imposes severe burden on the caregivers and can influence various aspects of

Microprocessor and Interfacing Essay Example for Free

Microprocessor and Interfacing Essay Peripherals and Interfacing PIO 8255 The parallel input-output port chip 8255 is also called as programmable peripheral input-output port. The Intel’s 8255 is designed for use with Intel’s 8-bit, 16-bit and higher capability microprocessors. It has 24 input/output lines which may be individually programmed in two groups of twelve lines each, or three groups of eight lines. The two groups of I/O pins are named as Group A and Group B. Each of these two groups contains a subgroup of eight I/O lines called as 8-bit port and another subgroup of four lines or a 4-bit port. Thus Group A contains an 8-bit port A along with a 4-bit port. C upper. PIO 8255 †¢ The port A lines are identified by symbols PA0-PA7 while the port C lines are identified as PC4-PC7. Similarly, GroupB contains an 8-bit port B, containing lines PB0-PB7 and 4-bit port C with lower bits PC0- PC3. The port C upper and port C lower can be used in combination as an 8-bitport C. †¢ Both the port C are assigned the same address. Thus one may have either three 8-bit I/O ports or two 8-bit and two 4-bit ports from 8255. All of these ports can function independently either as input or as output ports. This can be achieved by programming the bits of an internal register of 8255 called as control word register ( CWR ). PIO 8255 †¢ The internal block diagram and the pin configuration of 8255 are shown in fig. †¢ The 8-bit data bus buffer is controlled by the read/write control logic. The read/write control logic manages all of the internal and external transfers of both data and control words. †¢ RD, WR, A1, A0 and RESET are the inputs provided by the microprocessor to the READ/ WRITE control logic of 8255. The 8-bit, 3-state bidirectional buffer is used to interface the 8255 internal data bus with the external system data bus. PIO 8255 †¢ This buffer receives or transmits data upon the execution of input or output instructions by the microprocessor. The control words or status information is also transferred through the buffer. †¢ The signal description of 8255 are briefly presented as follows : †¢ PA7-PA0: These are eight port A lines that acts as either latched output or buffered input lines depending upon the control word loaded into the control word register. †¢ PC7-PC4 : Upper nibble of port C lines. They may act as either output latches or input buffers lines. PIO 8255 This port also can be used for generation of handshake lines in mode 1 or mode 2. †¢ PC3-PC0 : These are the lower port C lines, other details are the same as PC7-PC4 lines. †¢ PB0-PB7 : These are the eight port B lines which are used as latched output lines or buffered input lines in the same way as port A. †¢ RD : This is the input line driven by the microprocessor and should be low to indicate read operation to 8255. †¢ WR : This is an input line driven by the microprocessor. A low on this line indicates write operation. PIO 8255 †¢ CS : This is a chip select line. If this line goes low, it enables the 8255 to respond to RD and WR signals, otherwise RD and WR signal are neglected. †¢ A1-A0 : These are the address input lines and are driven by the microprocessor. These lines A1-A0 with RD, WR and CS from the following operations for 8255. These address lines are used for addressing any one of the four registers, i. e. three ports and a control word register as given in table below. †¢ In case of 8086 systems, if the 8255 is to be interfaced with lower order data bus, the A0 and A1 pins of 8255 are connected with A1 and A2 respectively. RD 0 0 0 0 RD 1 1 1 1 RD X 1 WR 1 1 1 1 WR 0 0 0 0 WR X 1 CS 0 0 0 0 CS 0 0 0 0 CS 1 0 A1 0 0 1 1 A1 0 0 1 1 A1 X X A0 0 1 0 1 A0 0 1 0 1 A0 X X Input (Read) cycle Port A to Data bus Port B to Data bus Port C to Data bus CWR to Data bus Output (Write) cycle Data bus to Port A Data bus to Port B Data bus to Port C Data bus to CWR Function Data bus tristated Data bus tristated Control Word Register PIO 8255. †¢ D0-D7 : These are the data bus lines those carry data or control word to/from the microprocessor. †¢ RESET : A logic high on this line clears the control word register of 8255. All ports are set as input ports by default after reset. Block Diagram of 8255 (Architecture) ( cont.. ) †¢ 1. 2. 3. 4. †¢ It has a 40 pins of 4 groups. Data bus buffer Read Write control logic Group A and Group B controls Port A, B and C Data bus buffer: This is a tristate bidirectional buffer used to interface the 8255 to system databus. Data is transmitted or received by the buffer on execution of input or output instruction by the CPU. Control word and status information are also transferred through this unit. †¢ Block Diagram of 8255 (Architecture) ( cont.. ) Read/Write control logic: This unit accepts control signals ( RD, WR ) and also inputs from address bus and issues commands to individual group of control blocks ( Group A, Group B). †¢ It has the following pins. a) CS Chipselect : A low on this PIN enables the communication between CPU and 8255. b) RD (Read) A low on this pin enables the CPU to read the data in the ports or the status word through data bus buffer. †¢ Block Diagram of 8255 (Architecture) ( cont.. ) WR ( Write ) : A low on this pin, the CPU can write data on to the ports or on to the control register through the data bus buffer. ) RESET: A high on this pin clears the control register and all ports are set to the input mode e) A0 and A1 ( Address pins ): These pins in conjunction with RD and WR pins control the selection of one of the 3 ports. †¢ Group A and Group B controls : These block receive control from the CPU and issues commands to their respective ports. c) Block Diagram of 8255 (Architecture) ( cont.. ) †¢ Group A PA and PCU ( PC7 -PC4) †¢ Group B PCL ( PC3 PC0) †¢ Control word register can only be written into no read operation of the CW register is allowed. a) Port A: This has an 8 bit latched/buffered O/P and 8 bit input latch. It can be programmed in 3 modes mode 0, mode 1, mode 2. b) Port B: This has an 8 bit latched / buffered O/P and 8 bit input latch. It can be programmed in mode 0, mode1. Block Diagram of 8255 (Architecture). c) Port C : This has an 8 bit latched input buffer and 8 bit out put latched/buffer. This port can be divided into two 4 bit ports and can be used as control signals for port A and port B. it can be programmed in mode 0. Modes of Operation of 8255 (cont.. ) †¢ These are two basic modes of operation of 8255. I/O mode and Bit Set-Reset mode (BSR). †¢ In I/O mode, the 8255 ports work as programmable I/O ports, while in BSR mode only port C (PC0-PC7) can be used to set or reset its individual port bits. †¢ Under the I/O mode of operation, further there are three modes of operation of 8255, so as to support different types of applications, mode 0, mode 1 and mode 2. Modes of Operation of 8255 (cont.. ) †¢ BSR Mode: In this mode any of the 8-bits of port C can be set or reset depending on D0 of the control word. The bit to be set or reset is selected by bit select flags D3, D2 and D 1 of the CWR as given in table. I/O Modes : a) Mode 0 ( Basic I/O mode ): This mode is also called as basic input/output mode. This mode provides simple input and output capabilities using each of the three ports. Data can be simply read from and written to the input and output ports respectively, after appropriate initialisation. D3 0 0 0 0 1 1 1 1 D2 0 0 1 1 0 0 1 1 D1 0 1 0 1 0 1 0 1 Selected bit s of port C D0 D1 D2 D3 D4 D5 D6 D7 BSR Mode : CWR Format PA 8 2 5 5 PCU PCL PA6 PA7 PC4 PC7 PC0-PC3 PB PB0 PB7 8 2 5 5 PA PCU PCL PB PA PC PB0 PB7 All Output Port A and Port C acting as O/P. Port B acting as I/P Mode 0 Modes of Operation of 8255 (cont.. ) †¢ 1. The salient features of this mode are as listed below: Two 8-bit ports ( port A and port B )and two 4-bit ports (port C upper and lower ) are available. The two 4-bit ports can be combinedly used as a third 8-bit port. Any port can be used as an input or output port. Output ports are latched. Input ports are not latched. A maximum of four ports are available so that overall 16 I/O configuration are possible. All these modes can be selected by programming a register internal to 8255 known as CWR. 2. 3. 4. †¢ Modes of Operation of 8255 (cont.. †¢ The control word register has two formats. The first format is valid for I/O modes of operation, i. e. modes 0, mode 1 and mode 2 while the second format is valid for bit set/reset (BSR) mode of operation. These formats are shown in following fig. D7 1 D6 X D5 X D4 X D3 D2 D1 D0 0- Reset 0-for BSR mode Bit select flags D3, D2, D1 are from 000 to 111 for bits PC0 TO PC71- Set I/O Mode Control Word Register Format and BSR Mode Control Word Register Format PA3 PA2 PA1 PA0 RD CS GND A1 A0 PC7 PC6 PC5 PC4 PC0 PC1 PC2 PC3 PB0 PB1 PB2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 0 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 PA4 PA5 PA6 PA7 WR Reset D0 D1 D2 D3 D4 D5 D6 D7 Vcc PB7 PB6 PB5 PB4 PB3 8255A 8255A Pin Configuration = D0-D7 CS RESET 8255A A0 A1 RD PA0-PA7 PC4-PC7 PC0-PC3 PB0-PB7 Vcc WR GND Signals of 8255 3 Group A control 1 D0-D7 Data bus Buffer 8 bit int data bus 4 Group A Port A(8) PA0-PA7 Group A Port C upper(4) Group B Port C Lower(4) PC7-PC4 PC0-PC3 2 RD WR A0 A1 RESET CS Block Diagram of 8255 READ/ WRITE Control Logic Group B control PB7-PB0 Group B Port B(8) D7 D6 D5 Mode for Port A D4 PA D3 PC U D2 Mode for PB D1 PB D0 PC L Mode Set flag 1- active 0- BSR mode Group A 1 Input PC u 0 Output 1 Input PA 0 Output 00 mode 0 Mode 01 mode 1 Select of PA 10 mode 2 Group B PCL PB Mode Select 1 Input 0 Output 1 Input 0 Output 0 mode- 0 1 mode- 1 Control Word Format of 8255 Modes of Operation of 8255 (cont.. ) b) Mode 1: ( Strobed input/output mode ) In this mode the handshaking control the input and output action of the specified port. Port C lines PC0-PC2, provide strobe or handshake lines for port B. This group which includes port B and PC0-PC2 is called as group B for Strobed data input/output. Port C lines PC3-PC5 provide strobe lines for port A. This group including port A and PC3-PC5 from group A. Thus port C is utilized for generating handshake signals. The salient features of mode 1 are listed as follows: Modes of Operation of 8255 (cont.. ) 1. 2. 3. 4. Two groups group A and group B are available for strobed data transfer. Each group contains one 8-bit data I/O port and one 4-bit control/data port. The 8-bit data port can be either used as input and output port. The inputs and outputs both are latched. Out of 8-bit port C, PC0-PC2 are used to generate control signals for port B and PC3-PC5 are used to generate control signals for port A. he lines PC6, PC7 may be used as independent data lines. Modes of Operation of 8255 (cont.. ) †¢ The control signals for both the groups in input and output modes are explained as follows: Input control signal definitions (mode 1 ): †¢ STB( Strobe input ) If this lines falls to logic low level, the data available at 8-bit input port is loaded into input latches. †¢ IBF ( Input buffer full ) If this signal rises to logic 1, it indicates that data has been loaded into latches, i. e. it works as an acknowledgement. IBF is set by a low on STB and is reset by the rising edge of RD input. Modes of Operation of 8255 (cont.. ) †¢ INTR ( Interrupt request ) This active high output signal can be used to interrupt the CPU whenever an input device requests the service. INTR is set by a high STB pin and a high at IBF pin. INTE is an internal flag that can be controlled by the bit set/reset mode of either PC4 (INTEA) or PC2(INTEB) as shown in fig. †¢ INTR is reset by a falling edge of RD input. Thus an external input device can be request the service of the processor by putting the data on the bus and sending the strobe signal. Modes of Operation of 8255 (cont.. Output control signal definitions (mode 1) : †¢ OBF (Output buffer full ) This status signal, whenever falls to low, indicates that CPU has written data to the specified output port. The OBF flip-flop will be set by a rising edge of WR signal and reset by a low going edge at the ACK input. †¢ ACK ( Acknowledge input ) ACK signal acts as an acknowledgement to be given by an output device. ACK sig nal, whenever low, informs the CPU that the data transferred by the CPU to the output device through the port is received by the output device. Modes of Operation of 8255 (cont.. ) †¢ INTR ( Interrupt request ) Thus an output signal that can be used to interrupt the CPU when an output device acknowledges the data received from the CPU. INTR is set when ACK, OBF and INTE are 1. It is reset by a falling edge on WR input. The INTEA and INTEB flags are controlled by the bit set-reset mode of PC 6and PC2 respectively. 1 0 1 0 Input control signal definitions in Mode 1 1/0 X X X 1 X X X X 1 1 X D7 D6 D5 D4 D3 D2 D1 D0 1 Input 0 Output For PC6 PC7 PA0 PA7 INTEA PC4 PC5 STBA IBFA D7 D6 D5 D4 D3 D2 D1 D0 PB0 PB7 INTEB PC 2 PC1 STBB IBFB PC3 RD PC6 PC7 INTRA I/O PC0 INTR A Mode 1 Control Word Group A I/P RD Mode 1 Control Word Group B I/P STB IBF INTR RD DATA from Peripheral Mode 1 Strobed Input Data Transfer WR OBF INTR ACK Data OP to Port Mode 1 Strobed Data Output Output control signal definitions Mode 1 1 0 1 0 1/0 X X X 1 X X X X 1 0 X D7 D6 D5 D4 D3 D2 D1 D0 1 Input 0 Output For PC4 PC5 PA0 PA7 INTEA PC7 PC6 OBF ACKA D7 D6 D5 D4 D3 D2 D1 D0 PB0 PB7 INTEB PC PC2 1 OBFB ACKB PC3 WR PC4 PC5 PC0 INTRA I/O INTRB Mode 1 Control Word Group A Mode 1 Control Word Group B Modes of Operation of 8255 (cont.. ) †¢ Mode 2 ( Strobed bidirectional I/O ): This mode of operation of 8255 is also called as strobed bidirectional I/O. This mode of operation provides 8255 with an additional features for communicating with a peripheral device on an 8-bit data bus. Handshaking signals are provided to maintain proper data flow and synchronization between the data transmitter and receiver. The interrupt generation and other functions are similar to mode 1. †¢ In this mode, 8255 is a bidirectional 8-bit port with handshake signals. The RD and WR signals decide whether the 8255 is going to operate as an input port or output port. Modes of Operation of 8255 (cont.. ) †¢ 1. 2. 3. 4. 5. The Salient features of Mode 2 of 8255 are listed as follows: The single 8-bit port in group A is available. The 8-bit port is bidirectional and additionally a 5-bit control port is available. Three I/O lines are available at port C. ( PC2 PC0 ) Inputs and outputs are both latched. The 5-bit control port C (PC3-PC7) is used for generating / accepting handshake signals for the 8-bit data transfer on port A. Modes of Operation of 8255 (cont.. ) †¢ Control signal definitions in mode 2: †¢ INTR (Interrupt request) As in mode 1, this control signal is active high and is used to interrupt the microprocessor to ask for transfer of the next data byte to/from it. This signal is used for input ( read ) as well as output ( write ) operations. †¢ Control Signals for Output operations: †¢ OBF ( Output buffer full ) This signal, when falls to low level, indicates that the CPU has written data to port A. Modes of Operation of 8255 (cont.. ) ACK ( Acknowledge ) This control input, when falls to logic low level, acknowledges that the previous data byte is received by the destination and next byte may be sent by the processor. This signal enables the internal tristate buffers to send the next data byte on port A. †¢ INTE1 ( A flag associated with OBF ) This can be controlled by bit set/reset mode with PC6 . †¢ Control signals for input operations : †¢ STB (Strobe inp ut ) A low on this line is used to strobe in the data into the input latches of 8255. Modes of Operation of 8255 (cont.. ) †¢ IBF ( Input buffer full ) When the data is loaded into input buffer, this ignal rises to logic ‘1’. This can be used as an acknowledge that the data has been received by the receiver. †¢ The waveforms in fig show the operation in Mode 2 for output as well as input port. †¢ Note: WR must occur before ACK and STB must be activated before RD. WR OBF INTR ACK STB IBF Data bus RD Mode 2 Bidirectional Data Transfer Data from 8085 Data towards 8255 Modes of Operation of 8255 (cont.. ) †¢ The following fig shows a schematic diagram containing an 8-bit bidirectional port, 5-bit control port and the relation of INTR with the control pins. Port B can either be set to Mode 0 or 1 with port A( Group A ) is in Mode 2. Mode 2 is not available for port B. The following fig shows the control word. †¢ The INTR goes high only if either IBF, INTE2, STB and RD go high or OBF, INTE1, ACK and WR go high. The port C can be read to know the status of the peripheral device, in terms of the control signals, using the normal I/O instructions. D7 1 D6 1 D5 X D4 X D3 X D2 1/0 D1 1/0 D0 1/0 1/0 mode Port A mode 2 Port B mode 0-mode 0 1- mode 1 PC2 PC0 1 Input 0 Output Port B 1- I/P 0-O/P Mode 2 control word PC3 PA0-PA7 INTR INTE 1 PC7 PC6 OBF ACK STB IBF 3 I/O INTE 2 RD WR PC4 PC5 Mode 2 pins