Flip Flop Circuit Explanation and Study

Flip Flop Circuit Explanation and Study A flip-flop is a term referring to an electronic circuit (a bistable multivibrator) that has two stable states and thereby is capable of serving as one bit of memory. Today, the term flip-flop has come to mostly denote non-transparent (clocked or edge-triggered) devices, while the simpler transparent ones are often referred to as latches; however, as this distinction is quite new, the two words are sometimes used interchangeably . A flip-flop is usually controlled by one or two control signals and/or a gate or clock signal. The output often includes the complement as well as the normal output. As flip-flops are implemented electronically, they require power and ground connections. Introduction Basic Flip-Flop Circuit A flip-flop circuit can be constructed from two NAND gates or two NOR gates. Each flip-flop has two outputs, Q and Q, and two inputs, set and reset. This type of flip-flop is referred to as an SR flip-flop or SR latch. The flip-flop in figure has two useful states. When Q=1 and Q=0, it is in the set state (or 1-state). When Q=0 and Q=1, it is in the clear state (or 0-state). The outputs Q and Q are complements of each other and are referred to as the normal and complement outputs, respectively. The binary state of the flip-flop is taken to be the value of the normal output. When a 1 is applied to both the set and reset inputs of the flip-flop in Figure 2, both Q and Q outputs go to 0. This condition violates the fact that both outputs are complements of each other. In normal operation this condition must be avoided by making sure that 1s are not applied to both inputs simultaneously. The NAND basic flip-flop circuit in figure operates with inputs normally at 1 unless the state of the flip-flop has to be changed. A 0 applied momentarily to the set input causes Q to go to 1 and Q to go to 0, putting the flip-flop in the set state. When both inputs go to 0, both outputs go to 1. This condition should be avoided in normal operation. Master-Slave Flip-Flop Introduction A master-slave flip-flop is constructed from two seperate flip-flops. One circuit serves as a master and the other as a slave. The logic diagram of an SR flip-flop is shown in figure.The master flip-flop is enabled on the positive edge of the clock pulse CP and the slave flip-flop is disabled by the inverter. The information at the external R and S inputs is transmitted to the master flip-flop. When the pulse returns to 0, the master flip-flop is disabled and the slave flip-flop is enabled. The slave flip-flop then goes to the same state as the master flip-flop. In addition to these two flip-flops, the circuit also includes an inverter. The inverter is connected to clock pulse in such a way that the inverted CP is given to the slave flip-flop. For example, if the CP=0 for a master flip-flop, then the output of the inverter is 1, and this value is assigned to the slave flip-flop. In other words if CP=0 for a master flip-flop, then CP=1 for a slave flip-flop. A master-slave flip flop can be constructed using any type of flip-flop which forms a combination with a clocked RS flip-flop, and with an inverter as slave circuit. An RS master-slave flip-flop consists of two RS flip-flops; one is the master flip-flop and the other a slave. The inverted CP is given to the slave flip-flop. Now when CP=0, the master flip-flop is disabled. So the external inputs R and S of the master flip-flop will not affect the circuit until CP goes to 1. The inverter output goes to 1 and it enables the slave flip-flop. The output Q=Y and Q=Y. When CP=1, the master flip-flop is enabled and the slave flip-flop remains isolated from the circuit until CP goes back to 0. Now Y and Y depends on the external inputs R and S of the master flip-flop. Assume that the flip-flop is in a clear state and no clock pulse is applied to the circuit. The external inputs given are S=1 and R=0. This input will not affect the state of the system until the CP=1. Now the next clock pulse applied should change the state to SET state (S=1, R=0). During the clock pulse transition from 0 to 1, the master flip-flop goes to set state and changes the output Y to 1. However this does not affect the output of the system since the slave flip-flop is isolated from the system (CP=0 for slave). So no change is observed at the output of the system. When the CP returns to 0, the master flip-flop is disabled while the slave is enabled. So the information from the master is allowed to pass through to the slave. Since Y=1, this changes the output Q to 1. In a master slave flip-flop it is possible to change the output of the flip-flop and the external input with same clock pulse. This is because the external input S can be changed at the same time while the pulse goes through its negative edge transition. When CP=0, change in external input S would not affect the state of the system. From this behavior of the master slave flip-flop it is quite clear that the state change in flip-flops coincide with the negative edge transition of the pulse. Negative edge transition means an inverter is attached between the CP terminal and the input of the slave. In positive edge triggered master slave flip-flops an additional inverter is attached between the CP terminal and the input of the master. Such flip-flops are triggered with negative pulses. Negative edge of the pulse affects the master and positive edge affects the slave. Timing Diagram The timing relationship is shown in figure and is assumed that the flip-flop is in the clear state prior to the occurrence of the clock pulse. The output state of the master-slave flip-flop occurs on the negative transition of the clock pulse. Some master-slave flip-flops change output state on the positive transition of the clock pulse by having an additional inverter between the CP terminal and the input of the master. Let us say that a clock of certain frequency is fed to the FF, and consider the case of JK being 11. The propagation delay of FF is very very less than the clock pulse time.The FF continues complementing the output an unpredictable number of times, thus leading to anomaly in the final output after the pulse time of the clock is completed.At the end the clock pulse, the value of O is uncertain.This continuous toggling of output when clock is HIGH is known asRace Around condition. This can be eliminated by Clock time should be less than the propagation delay time of the latch. By using Masterslave JK Flip flop. Pulse-Triggered Master-Slave These flip-flops are constructed from two separate flip-flops. The term pulse-triggered means that data are entered into the flip-flop on the leading edge of the clock pulse, but the output does not reflect the input state until the trailing edge of the clock pulse. This is due to the master flip-flop being rising edge triggered and the slave flip-flop being falling edge triggered as illustrated in the figure below. Master-Slave J-K Flip-Flop A master slave flip flop is a cascade of two S R flip flops with feedback from the outputs of the second to the inputs of the first. Positive clock pulses are applied to the first flip flop and clock pulses are inverted before these are applied to the second flip flop. The logic symbol for the master-slave flip-flop only indicates the initial inputs to the master and the outputs from the slave as indicated by the J-K master-slave flip-flop shown in figure Operation of master-slave J-k flip flop Whe CK=1, the first flip flop is enabled and the outputs Q and Q(toggle) respond to the J K according to its truth table.At this time the second flip flop is inhibited because its clock is LOW. When CK goes LOW, the first flip flop is inhibited and the second flip flop is enabled, because now its clock isHIGH.Since the second flip flop simply follows the first one it is referred to as slave and he first one as the master. Master-slave D flip-flop Consider the following terms: RIPPLE THROUGH: An input changes level during the clock period, and the change appears at the output. PROPAGATION DELAY: The time between applying a signal to an input, and the resulting change in the output. These problems can be overcome by masterslave D Flip flop. A master-slave D flip-flop is created by connecting two gated D latches in series, and inverting the enable input to one of them. It is called master-slave because the second latch in the series only changes in response to a change in the first (master) latch. The term pulse-triggered means that data is entered on the rising edge of the clock pulse, but the output does not reflect the change until the falling edge of the clock pulse. It responds on the negative edge of the enable input usually a clock. For a positive-edge triggered master-slave D flip-flop, when the clock signal is low (logical 0) the enable seen by the first or master D latch (the inverted clock signal) is high (logical 1). This allows the master latch to store the input value when the clock signal transitions from low to high. As the clock signal goes high (0 to 1) the inverted enable of the first latch goes low (1 to 0) and the value seen at the input to the master latch is locked. Nearly simultaneously, the twice inverted enable of the second or slave D latch transitions from low to high (0 to 1) with the clock signal. This allows the signal captured at the rising edge of the clock by the now locked master latch to pass through the slave latch. When the clock signal returns to low (1 to 0), the output of the slave latch is locked, and the value seen at the last rising edge of the clock is held while the master latch begins to accept new values in preparation for the next rising clock edge. By removing the leftmost inverter in the above circuit, a D-type flip flop that strobes on the falling edge of a clock signal can be obtained. The truth table obtained is as follows: CONVENTIONS: The circuit is set means output = 1 The circuit is reset means output = 0 Flip-flops have two output Q and Q or (Q and Q) Due to time related characteristic of the flip-flop, Q and Q (or Q) are usually represented as followed: Qt or Q: present state Qt+1 or Q+: next state POINTS TO REMEMBER: When using a real flip-flop, the following information is needed to be considered: propagation delay (tpLH, tpHL) time needed for an input signal to produce an output signal minimum pulse width (tw(min)) minimum amount of time a signal must be applied setup and hold time (tsu, th) minimum time the input signal must be held fixed before and after the latching action. USES: A flip-flop is used to store one bit, or binary digit, of data. Any one of the flip-flop types can be used to build any of the others. Many logic synthesis tools will not use any other type than D flip-flop and D latch. Level sensitive latches cause problems with Static Timing Analysis (STA) tools and Design For Test (DFT). Many FPGA devices contain only edge-triggered D flip-flops The data contained in several flip-flops may represent the state of a sequencer, the value of a counter, an ASCII character in a computers memory or any other piece of information. One use is to build finite state machines from electronic logic. The flip-flops remember the machines previous state, and digital logic uses that state to calculate the next state. Frequency division: a chain of T flip-flops as described above will also function to divide an input in frequency by 2n, where n is the number of flip-flops used between the input and the output. Master Slave Flip Flop is useful in eliminating race around condition. They are used in both asynchronous and clocked sequential systems.

Essay examples --

Edwin Blanco Eng 112 03/14/14 Oliver character analysis The novel Oliver Twist is about an orphan on the look for his true identity. During this search for selfhood Oliver comes into contact with the corruptive side of reality, eventually challenging his innocent character as a whole and leaving us to ask how does he remain pure and innocent in a cruel and corrupted place? In Charles Dickens’s novel, Oliver Twist the main theme is for to see if Oliver will maintain his innocence in a corrupt location like London. This idea of childhood represents children, such as Oliver Twist, as being innocent, but vulnerable to moral and criminal corruptions. The novel focuses on this idea by describing Oliver as a young, naà ¯ve, innocent child. Throughout the progression of the novel, Oliver is forced to deal with the gang of criminals like Fagin and the artful dodger. Oliver has to interpret their physical actions as being that of right or wrong. In this novel, Dickens wrote the character of Oliver Twist as a model of innocence. Olive r is a representation of a good person who people like Fagin and Bill Sikes try to corrupt but Oliver overcomes over their corruption of evil. Oliver is an important character in the novel because throughout his life he was treated horrible as if he was a criminal he has never seen what reality is like because he is being controlled. Oliver’s innocence is always being tested over and over, especially when he is introduced to the life of the criminal upon his arrival in London. In being raised as an orphan, Oliver did not have the opportunity to choose any aspect of his own life, but rather lived in a systematized environment where he was told what to do and when to do it and was given what he need in o... ...iver immediately recognizes it as an evil act. Oliver’s innocent and simple personality guarded him from these occurrences of wrongdoing. At first Oliver Twist is not aware of himself or of what is happening, but then is noticing what is happening is bad. Oliver’s innocence works to protect him from being affected by the criminal corruption seen and experienced through the criminal gang. Oliver is a character who is depicted as a naà ¯ve and innocent child. These personalities defend him from being fully aware of his surroundings. Throughout the entire novel Oliver encounters bad experiences with these criminals but he doesn’t change he still remains innocent and naà ¯ve. Oliver does not see the criminals the same way in which other people sees them, and it is this that allows Oliver to remain pure and innocent even with corruptive evils surrounding him.

Part Three Chapter VII

VII Up in the little white house that sat high above the town, Simon Price fretted and brooded. Days passed. The accusatory post had vanished from the message boards, but Simon remained paralysed. To withdraw his candidacy might seem like an admission of guilt. The police had not come knocking about the computer; Simon half regretted throwing it off the old bridge now. On the other hand, he could not decide whether he had imagined a knowing grin from the man behind the till when he handed over his credit card in the garage at the foot of the hill. There was a lot of talk about redundancies at work, and Simon was still afraid of the contents of that post coming to the bosses' ears, that they might save themselves redundancy pay by sacking himself, Jim and Tommy. Andrew watched and waited, losing hope every day. He had tried to show the world what his father was, and the world, it seemed, had merely shrugged. Andrew had imagined that someone from the printworks or the council would rise up and tell Simon firmly, ‘no'; that he was not fit to set himself up in competition with other people, that he was unsuitable and sub-standard, and must not disgrace himself or his family. Yet nothing had happened, except that Simon stopped talking about the council or making telephone calls in the hope of garnering votes, and the leaflets that he had had printed out of hours at work sat untouched in a box in the porch. Then, without warning or fanfare, came victory. Heading down the dark stairs in search of food on Friday evening, Andrew heard Simon talking stiffly on the telephone in the sitting room, and paused to listen. ‘†¦ withdraw my candidacy,' he was saying. ‘Yes. Well, my personal circumstances have changed. Yes. Yes. Yeah, that's right. OK. Thank you.' Andrew heard Simon replace the receiver. ‘Well, that's that,' his father said to his mother. ‘I'm well out of it, if that's the kind of shit they're throwing around.' He heard his mother return some muffled, approving rejoinder, and before Andrew had time to move, Simon had emerged into the hall below, drawn breath into his lungs and yelled the first syllable of Andrew's name, before realizing that his son was right in front of him. ‘What are you doing?' Simon's face was half in shadow, lit only by the light escaping the sitting room. ‘I wanted a drink,' Andrew lied; his father did not like the boys helping themselves to food. ‘You start work with Mollison this weekend, don't you?' ‘Yeah.' ‘Right, well, you listen to me. I want anything you can get on that bastard, d'you hear me? All the dirt you can get. And on his son, if you hear anything.' ‘All right,' said Andrew. ‘And I'll put it up on the fucking website for them,' said Simon, and he walked back into the sitting room. ‘Barry Fairbrother's fucking ghost.' As he scavenged an assortment of food that might not be missed, skimming off slices here, handfuls there, a jubilant jingle ran through Andrew's mind: I stopped you, you bastard. I stopped you. He had done exactly what he had set out to do: Simon had no idea who had brought his ambitions to dust. The silly sod was even demanding Andrew's help in getting his revenge; a complete about-turn, because when Andrew had first told his parents that he had a job at the delicatessen, Simon had been furious. ‘You stupid little tit. What about your fucking allergy?' ‘I thought I'd try not eating any of the nuts,' said Andrew. ‘Don't get smart with me, Pizza Face. What if you eat one accidentally, like at St Thomas's? D'you think we want to go through that crap again?' But Ruth had supported Andrew, telling Simon that Andrew was old enough to take care, to know better. When Simon had left the room, she had tried to tell Andrew that Simon was only worried about him. ‘The only thing he's worried about is that he'd have to miss bloody Match of the Day to take me to hospital.' Andrew returned to his bedroom, where he sat shovelling food into his mouth with one hand and texting Fats with the other. He thought that it was all over, finished, done with. Andrew had never yet had reason to observe the first tiny bubble of fermenting yeast, in which was contained an inevitable, alchemical transformation.

Dr. Morris s Hotel Rwanda - 1067 Words

Bojana Misljen POL 103: Intro to World Politics Dr. Morris Video Review Paper Hotel Rwanda The Rwandan genocide occurred in 1994 between the two prevalent ethnic groups in Rwanda, the Hutu and the Tutsi. Hotel Rwanda documents the plight of Paul Rusesabagina, a hotel manager, who opens his hotel as a shelter for the Tutsi people during the Rwandan genocide, saving thousands of lives in the processes. Through bribes Rusesabagina was able to keep thousands of Tutsi people from death. Like many other African states, Rwanda was colonized by a European superpower, Belgium. Therefore, many Rwandans blame Belgium for the division in the country because Belgium considered Tutsi to be more elegant; as a result Hutus were oppressed. After Rwanda†¦show more content†¦Hotel Rwanda demonstrates extreme violations of all articles in the UDHR, during the Rwanda Genocide towards the minority population, the Tutsi. During the genocide, Tutsis were forced to leave their homes in search of security. Unfortunately, so many Tutsi did not make to safety to the neighboring states. In th e Tutsi’s attempt to find safety, the Tutsi endured the agony of Hutu checkpoints who asked for identification; the identification cards were stamped by either a Hutu or Tutsi. The Tutsi were constantly discriminated and tormented by Hutus just because the Tutsi’s appearance did not meet the Hutu qualifications. For example, one Tutsi, in the movie, tell a story how their noses were measured to make sure that it met the Hutu qualifications. As a result, Tutsi women and children were raped and along with the men murdered. The Tutsi people were at times ordered to kill their own relatives, if they were not able to bribe the Hutu soldiers. The Tutsi neighborhoods were targeted; homes of the Tutsis were burglarized, destroyed, and burned. In the process, Hutus killed nearly 1 million Tutsis in less than one hundred days. Such acts violate the freedoms and right of individuals described in the articles of the UDHR. But especially the Rwanda Genocide was in breach of articl e thirty in the UDHR. The article thirty forbids a state from infringing on the rights of its citizens.