Interrupts and interrupt applications

Interrupts and interrupt applications 8086 Interrupts And Interrupt Applications Introduction: Microprocessors are computers built on single IC. There can be more ICs also used for this. Most microprocessors allow normal program execution to be interrupted by some external signal or by a special instruction in the program. In response to an interrupt the microprocessor stops executing its current program and calls a procedure which sevices the interrupt. An IRET instruction at the end of the interrupt service procedure returns execution to the interrupted program. 8086 Interrupts And Interrupt Responses: An 8086 interrupt can come from any one of three sources. One source is an external signal applied to the non-maskable interrupt (NMI) input pin or to the interrupt input pin. An interrupt caused by a signal    applied to one of these inputs is referred to as a hardware interrupt. A second source of an interrupt is execution of the interrupt instruction. This is referred to as a software interrupt. The third source of an interrupt is some error condition produced in the 8086 by the execution of an instruction. An example of this is the divide by zero interrupt. If you attempt to divide an operand by zero, the 8086 will automatically interrupt the currently executing program. At the end of each instruction cycle, the 8086 checks to see if any interrupts have been requested. If an interrupt has been requested, the 8086 responds to the interrupt by stepping through the following series of major actions: 1) It decrements the stack pointer by 2 and pushes the flag register on the stack. 2) It disables the 8086 INTR interrupt input by clearing the interrupt flag in the flag register. 3) It resets the trap flag in the flag register. 4) It decrements the stack pointer by 2 and pushes the current code segment register contents on the stack. 5) It decrements the stack pointer again by 2 and pushes the current instruction pointer contents on the stack. 8086 Interrupt Types: The preceding sections used the type 0 interrupts an example of how the 8086 interrupts function. It has hardware caused NMI interrupt, the software interrupts produced by the INT instruction, and the hardware interrupt produced by applying a signal to the INTR input pin. DIVIDE-BY-ZERO INTERRUPT-TYPE 0: The 8086 will automatically do a type 0 interrupt if the result of a DIV operation or an IDIV operation is too large to fit in the destination register. For   a type 0 interrupt, the 8086 pushes the flag register on the stack, resets IF and TF and pushes the return addresses on the stack. SINGLE STEP INTERRUPT-TYPE 1: The use of single step feature found in some monitor programs and debugger programs. When you tell a system to single step, it will execute one instruction and stop. If they are correct we can tell a system to single step, it will execute one instruction and stop. We can then examine the contents of registers and memory locations. In other words, when in single step mode a system will stop after it executes each instruction and wait for further direction from you. The 8086 trap flag and type 1 interrupt response make it quite easy to implement a single step feature direction. NONMASKABLE INTERRUPT-TYPE 2: The 8086 will automatically do a type 2 interrupt response when it receives a low to high transition on its NMI pin. When it does a type 2 interrupt, the 8086 will push the flags on the stack, reset TF and IF, and push the CS value and the IP value for the next instruction on the stack. It will then get the CS value for the start of the type 2 interrupt service procedure from address 0000AH and the IP value for the start of the procedure from address 00008H. BREAKPOINT INTERRUPT-TYPE 3: The type 3 interrupt is produced by execution of the INT3 instruction. The main use of the type 3 interrupt is to implement a breakpoint function in a system. When we insert a breakpoint, the system executes the instructions up to the breakpoint and then goes to the breakpoint procedure. Unlike the single step which stops execution after each instruction, the breakpoint feature executes all the instructions up to the inserted breakpoint and then stops execution. OVERFLOW INTERRUPT-TYPE4: The 8086 overflow flag will be set if the signed result of an arithmetic operation on two signed numbers is too large to be represented in the destination register or memory location. For example, if you add the 8 bit signed number 01101100 and the 8 bit signed number 010111101, the result will be 10111101. This would be the correct result if we were adding unsigned binary numbers, but it is not the correct signed result. SOFTWARE INTERRUPTS-TYPE O THROUGH 255: The 8086 INT instruction can be used to cause the 8086 to do any one of the 256 possible interrupt types. The desired interrupt type is specified as part of the instruction. The instruction INT32, for example will cause the 8086 to do a type 32 interrupt response. The 8086 will push the flag register on the stack, reset TF and IF, and push the CS and IP values of the next instruction on the stack. INTR INTERRUPTS-TYPES 0 THROUGH 255: The 8086 INTR input allows some external signal to interrupt execution of a program. Unlike the NMI input, however, INTR can be masked so that it cannot cause an interrupt. If the interrupt flag is cleared, then the INTR input is disabled. IF can be cleared at any time with CLEAR instruction. PRIORITY OF 8086 INTERRUPTS: If two or more interrupts occur at the same time   then the highest priority interrupt will be serviced first, and then the next highest priority interrupt will be serviced. As a example suppose that the INTR input is enabled, the 8086 receives an INTR signal during the execution of a divide instruction, and the divide operation produces a divide by zero interrupt. Since the internal interrupts-such as divide error, INT, and INTO have higher priority than INTR the 8086 will do a divide error interrupt response first. Hardware Interrupt Applications: Simple Interrupt Data Input: One of the most common uses of interrupts is to relieve a CPU of the burden of polling. To refresh your memory polling works as follows. The strobe or data ready signal from some external device is connected to an input port line on the microcomputer. The microcomputer uses a program loop to read and test this port line over and over until the data ready signal is found to be asserted. The microcomputer then exits the polling loop and reads in the data from the external device. The disadvantage of polled input or output is that while the microcomputer is polling the strobe or data ready signal, it cannot easily be doing other tasks. I n this case the data ready or strobe signal is connected to an interrupt input on the microcomputer. The microcomputer then goes about doing its other tasks until it is interrupted by a data ready signal from the external device. An interrupt service procedure can read in or send out the desired data in a few microseconds and return execution to the int errupted program. The input and output operation then uses only a small percentage of the microprocessors time. Counting Applications: As a simple example of the use of an interrupt input for counting , suppose that we are using an 8086 to control a printed circuit board making machine in our computerized electronics factory. Further suppose that we want to detect each finished board as it comes out of the machine and to keep a count with the number of boards fed in. This way we can determine if any boards were lost in the machine. To do this count on an interrupt basis, all we have to do is to detect when a board passes out of the machine and send an interrupt signal to an interrupt input on the 8086. The interrupt service procedure for that input can simply increment the board count stored in a named memory location. To detect a board coming out of the machine, we use an infrared LED, a photoresistor and two conditioning gates. The LED is positioned over the track where the boards come out, and the photoresistor is positioned below the track. When no board is between the LED and the photoresistor, the light from t he LED will strike the photoresistor and turn it on. The collector of the photoresistor will then be low, as will the NMI input on the 8086. When a board passes between the LED and photoresistor, the light will not reach the photoresistor and turn it on. The collector of the photoresistor will then be low, as will the NMI input on the 8086. Timing Applications: In this it is shown that how delay loop could be used to set the time between microcomputer operations. In   the example there, we used a delay loop to take in data samples at 1 ms intervals. The obvious disadvantage of a delay loop is that while the microcomputer is stuck in the delay loop, it cannot easily be doing other useful work. In many cases a delay loop would be a waste of the microcomputers valuable time, so we use an interrupt approach. Suppose for example, that in our 8086 controlled printed circuit board making machine we need to check the ph of a solution approximately every 4 min. If we used a delay loop to count off the 4 min, either the 8086 wouldnt be able to do much else or what points in the program to go check the ph. 8254 Software-Programmable Timer/Counter: Because of many tasks that they can be used for in microcomputer systems, programmable timer/counters are very important for you to learn about. As you read through following sections, pay particular attention to the applications of this device in systems and the general procedures for initializing a programmable device such as 8254. Basic 8253 And 8254 Operation: The intel 8253 and 8254 each contain three 16 bit counters which can be programmed to operate in several different modes. The major differences are as follows: 1) The maximum input clock frequency for the 8253 is 2.6 MHz, the maximum clock frequency for the 8254 is 8MHz. 2) The 8254 has a read back feature which allows you to latch the count in all the counters and the status of the counter at any point. The 8253 does not have this read back feature. The big advantage of these counters, however, is that you can load a count in them, start them and stop them with instructions in your program. Such a device is said to be software programmable. 8259a Priority Interrupt Controller: In a small system, for example, we might read ASCII characters in from a keyboard on an interrupt basis; count interrupts from timer to produce a real time clock of second, minutes and hours and detect several emergency or job done conditions on an interrupt basis. Each of these interrupt applications requires a separate interrupt input. If we are working with an 8086 , we have problem here because the 8086 has only two interrupt inputs, NMI and INTR. If we save NMI for a power failure interrupt, this leaves only one input for all the other applications. For applications where we have interrupts from multiple sources, we use an external device called a priority interrupt controller. Software Interrupt Applications: The software interrupt instruction INT N can be used to test any type of interrupt procedure. For example to test a type 64 interrupt procedure without the need for external hardware, we can execute the instruction INT 64. Another important use of software interrupts is to call Basic Input Output System, or BIOS, procedures in an IBM PC-type computer. These procedures in the system ROMS perform specific input or output functions, such as reading a character from the keyboard, writing some characters to the CRT, or reading some information from a disk. To call one of these procedures, you load any required parameters in some specified registers and execute an INT N instruction. N in this case is the interrupt type which vectors to the desired procedure. Suppose that, as part of an assembly language program that you are writing to run on an IBM PC type computer, you want to send some characters to the printer. The header for the INT 17H procedure from the IBM PC BIOS listing. The DX, AH, and AL registers are used to pass the required parameters to the procedure. The procedure is used for two different operations: initializing the printer port and sending a character to the printer. The operation performe d by the procedure is determined by the number passed to the procedure in the AH register. AH=1 means initialize the printer port, AH=0 means print the characters in AL, and AH=2 means read the printer status and returned in AH. If an attempt to print a character was not successful for some reason, such as the printer not being turned on, not being selected, or being busy, 01 is returned in AH. The main advantage of calling procedures with software interrupts is that you dont need to worry about the absolute address where the procedure actually resides or about trying to link the procedure into your program. So at last every microcomputer system uses a variety of interrupts and this is all about 8086 interrupts and applications. Conclusion: Microprocessors are computers built on single IC. There can be more ICs also used for this. Most microprocessors allow normal program execution to be interrupted by some external signal or by a special instruction in the program. In response to an interrupt the microprocessor stops executing its current program and calls a procedure which sevices the interrupt. An IRET instruction at the end of the interrupt service procedure returns execution to the interrupted program. An 8086 interrupt can come from any one of three sources. One source is an external signal applied to the non-maskable interrupt (NMI) input pin or to the interrupt input pin. An interrupt caused by a signal  Ã‚   applied to one of these inputs is referred to as a hardware interrupt. A second source of an interrupt is execution of the interrupt instruction. This is referred to as a   software interrupt. The third source of an interrupt is some error condition produced in the 8086 by the execution of an instructio n. An example of this is the divide by zero interrupt. If you attempt to divide an operand by zero, the 8086 will automatically interrupt the currently executing program. At the end of each instruction cycle, the 8086 checks to see if any interrupts have been requested. One of the most common uses of interrupts is to relieve a CPU of the burden of polling. To refresh your memory polling works as follows. The strobe or data ready signal from some external device is connected to an input port line on the microcomputer. The microcomputer uses a program loop to read and test this port line over and over until the data ready signal is found to be asserted. The software interrupt instruction INT N can be used to test any type of interrupt procedure. For example to test a type 64 interrupt procedure without the need for external hardware, we can execute the instruction INT 64. So at last we conclude that every microcomputer system uses a variety of interrupts and this is all about 8086 int errupts and applications. References: 1) DOUGLAS V.HALL, â€Å"microprocessors and interfacing† TaMcGRaw-Hill edition 2) www.wikipedia.com 3) www.google.com

Short Story the Painted Door

The Painted Door Summary Short story A Painted Door written by Sinclair Ross is a story that hides many meanings. The intelligent usage of symbolism and comparisons also add to the amount of thought and understanding being put towards the overall picture. It is clear that the author is not only about telling the story, rather he focuses much more on the voice, setting, and symbolism of the piece. The story was relayed to the readers in third person; the author also being the narrator.This gives him much more power to portray images and descriptions that could not be shown any way else. â€Å"She went on blowing against the frosted pane, carefully elongating the clear place until it was oval-shaped and symmetrical. † In this particular statement he is making the readers think about why this is being done. The setting of the story allowed for a lot of symbolism to be used; it was an average farm in the midst of the winter season. Feature Article – Short Story  The Plane of the Sleeping BeautyA lot of white colors being described and the cold and emptiness were also to the author’s advantage. As John the farmer goes to visit his father for the evening, his wife Ann tries to hold him back. As the final decision is made by the male character, we are introduced time and time again to the cold and emptiness of the setting. These tools are the author’s way of telling us how she feels and to prepare us for what is to happen next. As Steven, a close friend comes over, Ann begins to pretty herself up.These are all things that build towards the ending; of Ann’s Affair and Steven’s Suicide. The painted Door is a very interesting short story considering its great usage of symbolism as well as its setting. The author does a good job in portraying to us not only happenings but feelings and emotions as well. â€Å"The leap of light and shadow sank, and a chill crept in again†¦Ã¢â‚¬  The Painted Door Cover Page Rationale While creating a cover page for short story The Painted Door by Sinclair Ross, I considered many elements.In the end I chose aspects of symbolism because they would be the most effective and powerful way to portray the meaning of the story, without giving away the ending. The color white was very significant throughout the entire story, whether it was snow or the paint Ann used. This is why I chose the main color to be white and the whole picture to be washed out and faded. The background picture was that of a cobweb, implementing the idea of old or lost. This is telling us that the love of Ann and John is as such.The wood as another background simply describes the setting; an old farm house â€Å"unpainted† which is the whole reason Ann begins to paint. The chain coming across the entire picture is a symbol of the connection between Ann and her husband John. Many links form a chain holding them together even if they both don’t realize it. If you look closely to the bottom right corner, you will notice there is a cat looking towards a faded couple in midst of a kiss. The cat is a representation of deception and slyness, whereas the couple represents the affair between Ann and Steven.By having the cat face towards that direction, it portrays the fact that the affair was a total act of deception. Overall, I think my picture is a accurate presentation and cover page to the story because of the specific choice of used symbolism, given examples and relation to the setting and plot. The fact that everything is faded together almost gives it a look as if it all were a memory, also adding taste to the story; being portrayed from the past. For all these reasons, I have made my picture look how it does. Works Sited Ross, Sinclair. The Painted Door. 1, 10

Timeline of the Russian Revolutions 1918

Raising The Minimum Wage - 2447 Words

The minimum wage is defined as the lowest compensation, by law, which an employer may pay his or her employees. In the United States, this monetary value is set by a collection of laws on the federal, state, and local levels. While state and local governments may choose to observe a higher minimum wage than the national minimum wage, the federal government ultimately controls the income of the nation’s lowest-earning employees. At the federal level, the minimum wage was last raised in 2009, from $6.55 to $7.25 per hour. Yet, since 2009, the minimum wage has stayed the same, while the cost of living continues to climb. For this reason, an initiative to raise the minimum wage has numerous supporters, whose key arguments are the reduction of poverty and the increase in efficiency. At the same time, however, opponents of raising the minimum wage claim that it would result in unemployment and would be harmful to businesses. Although their arguments are valid, proponents of raising the minimum wage fail to see the effects of an increase in labor costs on employers. With any cost, one party benefits while another party pays. Furthermore, a raise in minimum wage, and an increase in the cost of labor, will result in losses not only for the employer, but also for the employee. Therefore, for those members of society who fall below the poverty line, raising the current minimum wage will do more harm than good. In her essay titled â€Å"Minimum Wages,† former economics professor LindaShow MoreRelatedRaising The Minimum Wage? Essay1217 Words   |  5 PagesThe minimum wage is one of the most discussed issues around the country. Everyone has a different opinion if raising the minimum wage would help families across the country to have a better lifestyle or if would cause an unbalance in the economy. Democrats and Republicans have a different view on this issue, while Democrats supports raising the minimum wage by $15 an hour, Republicans have stated that they refuse increasing the wage because it would leave different factions of Americans outside ofRead MoreRaising Minimum Wage912 Words   |  4 PagesMinimum wage has long been a topic that has brought on many heated debates. It has been said over and over again that minimum wage should be raised. These people say that raising minimum wage only does good for people. However, I, along with many other people, believe this is wrong, and we should instead be making moves to keep minimum wage where it is. Raising minimum wage may provide some positive effects, but those positives only go on to be overwhelmed by the negative effects caused by it. WagesRead MoreRaising The Minimum Wage?1575 Words   |  7 PagesThe issue of raising the minimum wage from $7.25 to $15 an hour is a heavily debated topic. Both sources against or in favor of the minimum wage refer to a â€Å"growing gap† between low-income workers and high-income earners. Sources against the minimum wage believe raising it will increase this gap, whereas those in favor of the minimum wage believe it will decrease this gap. The arguments in favor of the minimum wage rely mostly on ethical beliefs, such as â€Å"pay should reflect hard work,† to advanceRead MoreRaising The Minimum Wage888 Words   |  4 Pages Raising the Minimum Wage The employment effect of the minimum wage is one of the most studied topics in all economics. Today, the debate over raising the minimum wage has been a hot topic after President Obama explained in his 2014 State of the Union address that he intends to raise the minimum wage from $7.25 to $10.10 per hour, an increase of over 40 percent. While the President and his supporters claim that this increase would greatly benefit the economy and result in growing the businessesRead MoreRaising The Minimum Wage?1122 Words   |  5 Pagesâ€Å"Raise the wage!† reads many protestors’ signs across America. Many people believe this to be the answer to the financial inequality that plagues our country. The federal minimum wage was established to keep workers from settling on a poor living standard (Leonard A.11). Since this was passed, multiple debates and issues have risen. One begins to ask the question, is this truly the best way to resolve the unequal distribution of wealth? Aft er research, it has been found that there are many drawbacksRead MoreRaising The Minimum Wage1979 Words   |  8 PagesResearch Raising the minimum wage can result in job losses due to lower profits for businesses. It can also potentially decrease employee hours by changing them from full time to part time. Additionally, it may reduce the full time benefits that they receive. If this were to happen, then the employees affected will actually be earning less than they did before the increase. For example, from the Article Maximum Divide on Minimum Wage (Mejeur, 2014), they state, â€Å"Labor costs are the largest shareRead MoreRaising The Minimum Wage?870 Words   |  4 PagesThe topic of raising the minimum wage has many different viewpoints. It is thought to be affected negatively and positively. Some believe it increases unemployment and poverty. Others believe it creates jobs, helps the economy and low-income families by giving them more money to give back to the economy. Doug Hall, director of the Economic Analysis and Research Network and David Cooper, Economic Analyst at the Economic Policy Institute, expressed how the increase in minimum wage affects certainRead MoreRaising The Minimum Wage1037 Words   |  5 PagesRaising the minimum wage from $7.25 to $10.10 is not a good idea. The unintended consequences that would come about as a result is reason enough to shy away from such a proposal. Those who support an increase contend that it will alleviate poverty. Suppose these advocates are right and a spike in the minimum wage does reduce poverty for some fortunate workers. This positive development will be offset because an increase in the minimum wage will further price out inexperienced workers from the jobRead MoreRaising The Minimum Wage1864 Words   |  8 Pagespersevere, and really believe in yourself, good things will come. Drastically raising the minimum wage goes against all of those principles, rewarding lethargic actions and poor life c hoices. Raising the minimum wage to $15 will do more harm than good for middle class americans by decreasing the value of the money in their pockets, driving out big companies, and generally increasing unemployment. Increasing the minimum wage causes middle class Americans have less money in their pockets to spend. RepresentativesRead MoreEffect Of Raising Minimum Wage1215 Words   |  5 PagesEffects of Raising Minimum Wage The minimum wage in this country has been a controversial issue. Many people believe it will help reduce poverty and boost the economy. However, they are not looking at the downfalls this will bring to our country. This could make the unemployment population rise, it will raise prices of other things, and would have little effect on reducing poverty. Raising the minimum wage would have a negative influence on our country. This movement throughout our country