Conjugating the French Verb Souffrir (to Suffer)

Souffrir  (to suffer, to endure, to tolerate, to be in pain) is an  irregular French  -ir  verb. Below are simple  conjugations  of the verb  souffrir; the conjugation table does not include compound tenses, which consist of  a form of the auxiliary verb  avoir  with the past participle  souffert. Within irregular  -ir  verb conjugations, there are some  patterns. Two groups exhibit similar characteristics and conjugation patterns. Then there is a final, large category of extremely irregular  -ir  verbs that follow no pattern. Souffrir IS AN IRREGULAR -IR- VERB Soufrir  lies in the second group of irregular  -ir  verbs that display a pattern. The second group of verbs includes verbs like souffrir that all end in -frir  or  -vrir. These verbs, surprisingly,  are all  conjugated like  regular  -er  verbs. Souffrir IS CONJUGATED LIKE VERBS ENDING IN -FRIR AND -VRIR All French verbs that end in  -frir  or  -vrir  are conjugated this way. They include: couvrir   to covercueillir   to pickdà ©couvrir   to discoverentrouvrir to half-openouvrir   to openoffrir   to offerrecouvrir   to recover, conceal  rouvrir   to reopen EXPRESSIONS AND USAGE souffrir  en silence   to suffer in silenceSi tu avais souffert ce que jai souffert  !   If youd suffered as much as I have !,  if you had gone through what I have !Elle ne souffre pas dà ªtre critiquà ©e  /  quon la critique.   She cant stand  /  take criticismTu souffres  ?  Ã‚  Are you in pain ? Does it hurt ?souffrir de   to suffer fromsouffrir des dents   to have trouble with ones teeth  souffrir le martyr   to suffer agoniesSon dos lui fait souffrir le martyre. He has terrible trouble with his back.faire souffrir quelquun   to make someone  suffer  Ã‚  ne pas pouvoir souffrir quelquun to not be able to bear someoneJe ne peux souffrir cette idà ©e.  Ã‚  I cant bear the thoughtIl ne peut pas la souffrir.  Ã‚  He cant bear her.  Ã‚  souffrir  inutilement   to suffer needlessly  souffrir  financià ¨rement   to suffer financially / to be in bad straits financiallyOà ¹ souffrez-vous  ?   Where is the pain ? / Where does it hurt ?Elle a beaucoup souffert lors de son accouchement. She had a very painful delivery.Il est mort sans souffrir.   He felt no pain when he died.souffrir de la faim / soif  Ã‚  to suffer from hunger / thirstsouffrir de la chaleur   to suffer from the heatsouffrir de  (figurative):  Sa renommà ©e a souffert du scandale. His reputation suffered from the scandal.dà »t ton amour-propre en souffrir  Ã‚  even though your pride may sufferLes rà ©coltes nont pas trop souffert. The crops didnt suffer too much  /  werent too badly damaged.Cest le sud du pays qui a le plus souffert.   The southern part of the country was the hit the hardest.se souffrir (pronominal): Ils ne peuvent pas se souffrir. They cant stand  / bear each other. Simple Conjugations of the Irregular French -ir Verb Soufrir Present Future Imperfect Present participle je souffre souffrirai souffrais souffrant tu souffres souffriras souffrais il souffre souffrira souffrait nous souffrons souffrirons souffrions vous souffrez souffrirez souffriez ils souffrent souffriront souffraient Pass compos Auxiliary verb avoir Past participle souffert Subjunctive Conditional Pass simple Imperfect subjunctive je souffre souffrirais souffris souffrisse tu souffres souffrirais souffris souffrisses il souffre souffrirait souffrit souffrt nous souffrions souffririons souffrmes souffrissions vous souffriez souffririez souffrtes souffrissiez ils souffrent souffriraient souffrirent souffrissent Imperative tu souffre nous souffrons vous souffrez

Day after day, late students are punished or end up in...

Day after day, late students are punished or end up in detention due to short passing periods. Having short passing periods can make a student’s grade go down or worse when students are late to class. This can be prevented by extending passing periods to 10 minutes. Although the staff at H.P.M.S may disapprove, but in the long run, they will see the effects of having longer passing periods has on students. Because of the short time of passing periods, students at Happy Place Middle School are petitioning to extend their passing period time to 10 minutes. In short, some of the positive effects are that students can get to class on time, and gives students and teachers time to prepare. In addition to that, when the passing period time is†¦show more content†¦And also, the traffic in the halls often crawls at the SPEED OF MOLASSES. Simply to say, it can make you very late for class. â€Å"Students also go to their class missing their books because they don’t have time to go to the locker to get their materials. This makes it worse for students because they are unable to do work† (Abdelmalek). Furthermore into the topic, the 10 minute passing period lets and/or helps teachers prepare for their next period. A longer passing period would prevent students from asking to go use the bathroom, get a drink, or be late, so teacher(s) have the student’s full concentration, â€Å"If your student doesn’t have to interrupt you to use the restroom or get some water, it is going to be a better learning environment for the rest of the students. Without these interruptions you may continue your lesson and have student’s full concentration, instead of worrying about their personal needs† (Medina). And also in addition to that, teachers will have more time to prepare for their next class compared to 5 minutes, so teachers can get coffee or take a break during the passing period. Therefore, passing periods should be extended to 10 minutes since there are upsides and very few downsides, the upsides: Have more time to get to their classes, students can be spared fr om the worstShow MoreRelatedJuvenile Crime Issues in Today’s Criminal Justice System18893 Words   |  76 PagesIntroductory Text for the 21st Century, Eleventh Edition, by Frank Schmalleger. Published by Prentice Hall. Copyright  © 2011 by Pearson Education, Inc. The Future Comes One Day at a Time o one can truly say what the future holds. Will the supporters of individual rights or the advocates of public order ultimately claim the day? We cannot say for sure. This much is certain, however: Things change. The future system of American criminal justice will not be quite the same system we know today. Many ofRead MoreIndian Polity and Social Issue16628 Words   |  67 Pagesconstitutional amendment. India celebrates the adoption of the constitution on 26 January each year as Republic Day. It is the longest written constitution of any sovereign country in the world, containing 395 articles in 22 parts, 12 schedules and 94 amendments, for a total of 117,369 words in the English language version. Besides the English version, there is an official Hindi translation. After coming into effect, the Constitution replaced the Government of India Act 1935 as the governing document ofRead MoreDeveloping Management Skills404131 Words   |  1617 PagesPsychological Resiliency 139 Social Resiliency 143 Temporary Stress-Reduction Techniques 144 SKILL ANALYSIS 147 Cases Involving Stress Management 147 The Turn of the Tide 147 The Case of the Missing Time 150 SKILL PRACTICE 155 Exercises for Long-Term and Short-Run Stress Management The Small-Wins Strategy 155 Life-Balance Analysis 156 Deep Relaxation 158 Monitoring and Managing Time 159 SKILL APPLICATION 161 Activities for Managing Stress 161 Suggested Assignments 161 Application Plan and Evaluation 162

Analysis Of Two Bush Speeches - Free Essay Example

Sample details Pages: 5 Words: 1528 Downloads: 1 Date added: 2019/10/31 Category Society Essay Level High school Topics: Gulf War Essay Did you like this example? Presidents play a critical role when influencing the public through the use of rhetoric. Through only words often within a speech a president can have an everlasting impact on society and the public. Rhetoric, and how its used, is arguably one of the most powerful and unique dynamics of a presidency. Don’t waste time! Our writers will create an original "Analysis Of Two Bush Speeches" essay for you Create order Presidential rhetoric is so powerful that it can even incite war and rationalize its indispensability. For decades presidents have been using their platform to push their personal political agendas within their rhetoric especially within war rhetoric. So, can presidents incite war through rhetoric solely? I argue, yes, that presidents can make war seem inevitable and incite war through their rhetoric alone. A resounding depiction of this use of rhetoric is found when looking at George H. W. Bushs rhetoric in 1990 1991 in regard to The Gulf War. George H. W. Bush stimulates, through rhetoric, the notion that The Gulf War (also known as Operation Desert Storm) was necessary. Consistent themes are found within presidential speeches that shape war rhetoric. Common themes are demonization of the opposition, human rights concerns, and defeating aggression. All of the themes mentioned are illustrated within Bushs rhetoric preceding and during The Gulf War. To illuminate these rhetorical t hemes and argue the incitation of war by George H. W. Bush I will be analyzing two of his speeches: Address on Iraqs Invasion of Kuwait and Announcing War on Iraq. Literature Review   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   War rhetoric, according to Jamieson and Campbell, means the rhetoric by which presidents seek to justify to Congress and to the citizenry their exercise of war powers. Presidential war rhetoric intends to launch invasions, direct invasions, suffice stationing troops, and sell the war. Its imperative to sell the war so that people will fight it and people will fund it. Presidential power, especially war power, has expanded and increased with every decade in respect to rhetoric. Executive war powers have been broadened over time by their exercise, by congressional complicity, and by Supreme Court sanction (Campbell and Jamieson, 2013). The president can overstep his assumed constitutional powers and rights through the use of rhetoric due to the blurred lines of what the president can and cant do. Rhetoric can subdue what might seem unconstitutional as far as influencing the nation or pushing a personal agenda. War rhetoric is a constant power struggle betwe en the President and Congress mediated by The Supreme Court. Presidential war rhetoric is related to the ongoing struggle between the president and Congress, refereed by the courts, over what the Constitution permits the president to do (Campbell and Jamieson, 2013). Presidential entitlements have been into argument because article 1 of the Constitution reserves to Congress the authority to declare War, . to raise and support Armies, . provide and maintain a Navy, . [and] make Rules for the Government and Regulation of the land and naval forces, whereas article 2 defines the president as Commander in Chief of the Army and Navy of the United States, and of the militia of the several states, when called into the actual service of the United States. (Campbell and Jamieson, 2013). The democratic solution to war includes 2 steps: 1) President must request or recommend declaration of war; 2) Congress must declare war through resolution, statute, or declaration of war. The argument of the President being able to take advantage of and exploit their power of war is validated through the evidence of only five officially declared wars. According to Campbell and Jamieson, major military actions in Korea, Vietnam, Kuwait, and Iraq have been carried out without declarations of war, and more than one hundred military ventures involving combat troops have been conducted without any form of congressional authorization. The majority of American wars have been enacted without statutory authorization, a resolution of support, or a declaration of war (Campbell and Jamieson, 2013). It is often argued whether or not a presidents call to war is appropriately in the defense of our nation or an overstep of the nations military capabilities. It is often in question if a presidential decision to go to war is a hasty or responsive decision, rather than a well thought out one. The founders hoped that the rhetorical process implied by the Constitution would ensure that a decision to wage war would be arrived at thoughtfully, not rashly or emotionally (Campbell and Jamieson, 2013). While it is often seen that a president is overstepping his congressional duties by inciting war, it is still a frequent occurrence that is provoked through rhetoric. Despite the change from former to subsequent reasoning of military action, Campbell and Jamieson argue that presidential war rhetoric throughout U.S. history manifests five pivotal characteristics: 1) every element in it proclaims that the momentous decision to resort to force is deliberate, the product of thoughtful consideration; 2) forceful intervention is justified through a chronicle or narrative from which argumentative claims are drawn; 3) the audience is exhorted to unanimity of purpose and total commitment; 4) the rhetoric not only justifies the use of force, but also seeks to legitimize presidential assumption of the extraordinary powers of the commander in chief; and, as a function of these other characteristics, 5) strategic misrepresentations play an unusually significant role in its appeals (Campbell and Jamieson, 2013). It is often found that by including these characteristics in their speeches, the President is better able to legitimatize his intentions in the interes t of the constitutional right to defend the nation. Within war rhetoric it is common for the President to greet his rational deliberation (a constitutional obligation) with recommending Congress to declare war or to authorize the introduction of armed forces (Campbell and Jamieson, 2013). This thoughtful deliberation usually is when the President states that he has talked to international leaders, allies, all of the government, etc. before speaking on the matter. Perhaps one of the most prominent and effective characteristics of war rhetoric is the use of narratives. Narratives are typically what allow the media to further the argument of war and influence the public. The use of narratives allows the President to dramatize and simplify the situation at hand so that war seems inevitable. Narratives often explore the idea of how alternatives might be possible but due to the [dramatic] situation or threat at hand an immediate response is undoubtedly necessary. The narrative typically reframes the conflict as aggression by the enemy, according to Jamieson and Campbell, which legitimizes presidential initiatives as actions to defend the nation. This type of narrative results in a call to action to support the decision to wage war. An extended narrative is often seen in war rhetoric, where the President structures the argument of war by exhausting national values to frame the opposition as a threat to the nation and civilization. War rhetoric narratives often characterizes America as innocent and in favor of good, desiring to help others or taking action in the best interest of others. Narratives tend to differ between presidents based on intentions and motives but remains an essential characteristic of war rhetoric. Following narratives is the third characteristic of presidential war rhetoric that Campbell and Jamieson discuss, exhortation to unified action. It is often found within presidential speeches that incite war elements of unification. This unification element is in large part due to framing the intent behind war being in the best interest of humanity and civilization as a whole. The concept of unification comes with the assumed [anticipative] conclusion that right will prevail (Campbell and Jamieson, 2013). This characteristic will often appear as a president reminding the audience to put parties aside and using unifying terms and phrases like we and my fellow Americans while playing on national values. Exhortation to unified action speaks to the values Americans want to see in themselves and suggests values are threatened. The fourth characteristic that Campbell and Jamieson designate as a necessary element of war rhetoric is investiture as commander in chief. Ultimately, war rhetoric is a rhetoric of investiture (Campbell and Jamieson, 2013) meaning that it is an [arguably] excusable time to expand power as a president and justify why. The president rationalizes this as the time to exercise his right to play the role of Commander in Chief due to the threat of American values and the community. While the original intent of the role Commander in Chief was to repel attack, presidential innovations have created precedents that presidents have used to claim expanded executive war powers (C ampbell and Jamieson, 2013). Another complex modification of this characteristic is the role Congress now plays with the president in waging war. The intent of the Constitution was that the president would go to Congress to request authorization to act as commander in chief, but now the president assumes the role and then asks for congressional ratification (Campbell and Jamieson, 2013). The characteristic that plays a very significant role in war rhetoric is strategic misrepresentation. Strategic misrepresentation is a very dominant trend within Bushs war rhetoric, which will be explored further in this paper. War rhetoric is typically intended to incite immediate action demanding immediate support. This urgent action is attainable through the use of strategic misrepresentation, where the president uses rhetoric to misrepresent the events described in ways strategically related to stifle dissent and unify the nation (Campbell and Jamieson, 2013).

Same Sex Parenting And Parents Essay - 975 Words

This paper discusses same-sex parenting and some of the situations they have experienced. I will be discussing how this same sex pair handles family life, their demographics in relation to class material and Family Systems Theory as well as personal and professional application in their situation. There are a number of same sex parents in society today. Same sex families are no different from other families, but there are a few unique challenges that occasionally arise. Same sex parents still have a very effective style of parenting. I can see how a child’s success still comes from the quality of the parent-child relationships. Demographics: It is difficult to attain a precise count of same-sex parent families in the United States today. I believe this is due to many same sex families are not open about their sexual orientation or family situation. The partners in my interview have been in a relationship for ten years. They have a single child that is a ten-year-old boy. They developed a relationship when the mother was four months pregnant. The mother is thirty-eight years old, and the partner is thirty-five. This relationship was the mother’s and partner’s second serious relationship. Relation to Class Material: This topic will discuss three subjects that I learned in class that relate to my interview questions and answers. The first subject discussed is the transition to parenthood, becoming a parent. This family is unique because the mother was going throughShow MoreRelatedâ€Å"The Changing Reality of the American Family- Same Sex Parenting â€Å" An estimated two million1000 Words   |  4 PagesFamily- Same Sex Parenting â€Å" An estimated two million children are being raised in a single or same sex parent in the United States. The exact number of children raised in this type home cannot be determined due to the secrecy resulting from the stigma associated with homosexuality (Perrin, Siegel 3). Families of same sex parents often resemble step families formed after heterosexual couples divorce. Due to social acceptance of diversity in sexual orientation (Perrin 2), same sex parenting is foreverRead MoreWhy Gay Men And Gay Couples Should Be Legal944 Words   |  4 PagesHow Gay Men and Lesbians Perform as Parents Compared to Heterosexual Couples Recently, controversies have been witnessed concerning the issues of gender and sexuality. For example, the US government has issued directives regarding the legality of same-sex relationships. Several states in America have legalized homosexuality while the others have remained adamant to accept such sexual orientations. 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There are even laws prohibiting same-sex couples from becoming adoptive parents altogether. Rights should not be limited because of sexual orientation, race, religion, gender, or cree d; that’s discrimination. Same-sex couples who want to be parents should haveRead More A Study on Gay Parenting Essay1090 Words   |  5 Pagesmovement towards equality of treatment and integration into society. One of these matters that has garnered attention is gay parenting. With some states now allowing same-sex marriage or unions, the next step being taken is starting a family. There has been wide speculation into sexual orientation and whether it has an impact on homosexuals and their abilities to be good parents. 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I know that I am strongly traditional in my theological views, nevertheless, I vigorously believe that traditional marriage and parenting are devotional commitments between a man and a woman. Therefore, same-sex marriage and parenting are to me, issues of a society with strong traditional cultural identities

Microprocessor and Interfacing Free Essays

string(187) " 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\." UNIT II- 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. We will write a custom essay sample on Microprocessor and Interfacing or any similar topic only for you Order Now 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. You read "Microprocessor and Interfacing" in category "Papers" †¢ Group A and Group B controls : These block receive control from the CPU and iss ues 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 latche s. †¢ 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 a n output device. ACK signal, 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 input ) 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 onl y 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 How to cite Microprocessor and Interfacing, Papers

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string(187) " 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\." UNIT II- 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. We will write a custom essay sample on Microprocessor and Interfacing or any similar topic only for you Order Now 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. You read "Microprocessor and Interfacing" in category "Papers" †¢ Group A and Group B controls : These block receive control from the CPU and iss ues 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 latche s. †¢ 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 a n output device. ACK signal, 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 input ) 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 onl y 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 How to cite Microprocessor and Interfacing, Papers

Jamestown Settlement free essay sample

The first permanent English colony in North America was established at Jamestown, Virginia, in 1607. In order to earn quick profits for Virginia Company investors, the settlers wasted no time and immediately began hunting for gold and searching for the Northwest Passage to Asia. According to page forty-two in the American Journey textbook, â€Å"all they would find was suffering and disappointment,† which would foreshadow the years ahead. The colony would soon prove to be an immediate disaster. First of all the settlers neglected to plant crops because they were so eager to find new riches. The colonists had never really planned to grow all of their own food. Instead, their plans depended upon trade with the local Native Americans to supply them with enough food between the arrival of periodic supply ships from England. This quickly caused their food supplies to dwindle and many starved to death. The second mistake the settlers made is that the settlement was located in a swamp. We will write a custom essay sample on Jamestown Settlement or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page This soon led to diseases caused by parasites that were there and malaria caused by all the mosquitoes. So the settlers that didn’t starve usually died from disease. Initially Captain John Smith saved the colony through his leadership by imposing order and military discipline. However, certain settlers refused to follow his orders and believed their social status exempted them from manual labor. Just as bad was the failure of the colonists to work together for the common good, or indeed to work at all. The impending hardship was further compounded by the loss of Smith, who became injured in August of 1609 in a gunpowder accident, and was forced to return to England for medical attention in October 1609. This proved to be a major blow because he was most skillful in dealing with the Indians in trading for food. For years there was hardship and suffering in Jamestown, but in 1619 three important developments occurred. The company began to tranport women to become the wives of the planters and intice them to stay in the colony. The same year the first Africans arrived in Virginia and soon became indentured servants. The last major happening was the company created the first legislative body in English America. They were told to establish one equal and uniform government over all Virginia. According to the textbook, this also set a precedent for the establishment of self-government in other English colonies. The early years for Jamestown were full of disappointment, suffering, starvation, and tribulations. There was a constant battle going on with the Powhatan Confederacy and the colonists. Over time the settlers lost the Virginia Company, but eventually had a successful colony thanks to an established government and a marketable tobacco crop. .