Single-chip-microcomputer-resetting-circuit-reliability-analysis.doc

Single-chip microcomputer resetting circuit reliability analysis Summary: summarizes the current use of a broader four Single-chip microcomputer spaces circuit for differential type, calculus-based mathematical models of spaces circuit created, and compares their use in the reliability, and introduced the spaces dedicated chip. Finally made circuit design of spaces should be noted and the measures to enhance sexual interference. Keyword : reliability of spaces crash Single-chip microcomputer have now been widely used in home appliances, medical, instrumentation, industrial automation, aerospace and other fields. Market more popular Single-chip microcomputer main types of Intel Corporation, Atmel Corporation and the 8051 series Single-chip microcomputer Philip Corporation, Motorola M6800 series Single-chip microcomputer companies, Intel Corporation MCS96 series Single-chip microcomputer and Microchip pic series Single-chip microcomputer companies. Whatever type of Single-chip microcomputerusers, the total of spaces to be involved Single-chip microcomputer circuit design. Single-chip microcomputer resetting circuit design and good or bad, directly affects the whole system reliability. End users in the design of many Single-chip microcomputer systems, and debugging successful in the laboratory, the scene has emerged in the crash and procedures to fly phenomena, mainly Single-chip microcomputer the circuit design of the spaces caused by unreliable. Viii Single-chip microcomputer with a large led display a power-sharing, and use of spaces differential circuit examples. In such cases, the system sometimes some unpredictable phenomena, such as erratic through the crash and procedures to fly. And the use of simulation device debugging when not occur or very rare phenomenon this phenomenon. As figure 2 shows, in this figure Single-chip microcomputer restoration of the spaces use another circuit. In this circuit application, users sometimes found again in a short period of time after the opening of closed power supply, Single-chip microcomputer may not work properly. These phenomena can be considered to be due to improper design Single-chip microcomputer resetting circuit caused. So far, Single-chip microcomputer circuit mainly four types of spaces : (1) differential type of spaces circuit; (2) scoring type of spaces circuit; (3) Comparison by type of spaces circuit; (4) The type of man spaces circuit. In addition, the company also launched a voice of the spaces devoted to the dedicated chip. 1 restoration circuit mathematical models and reliability analysis 1.1 differentiation type of spaces circuit Differential circuit equivalent circuit model of spaces shown in figure 3. To Gaodianping restoration, for example. Power, electricity, it that upon Us to Jieyue signal that. U0 which is due in CPU of spaces down resistance R-induced voltage value, generally 0.3V below. But in practical application, it is impossible for the ideal upon Us Jieyue signal. The main reason is twofold : 1 restoration circuit mathematical models and reliability analysis (1) The installed power output switches identity; (2) personnel in the design of circuit design, power supply voltage to ensure stability, often in parallel connection of a large power input-capacitance, leading to the signal upon Us impossible for Jieyue characteristics. Since the first case and the second case is essentially the same, namely, to have an impact upon Us upward slope, thereby affecting the urst the restoration identity. To leave upon us upward slope for k from t 0VUs need time, namely : When T advantage, the advantage A=T/ is : That the spaces at the front of reliability than goodA situation that is the nature of the design will be some switching power devices, such as power led and made it a Single-chip microcomputer system voltage power sharing, and Single-chip microcomputer system of spaces - spaces of a differential circuit, which will result in the anomaly of spaces. Will be equivalent to the resistance either device, which switches either large or small character that either two working condition. Voltage electrical work and the basic principles are : U- I RL I- U. As can be seen, the load current changes from the changes. To analyse simple assumption RRL and RR0. Thus, she can be similar to the above circuit network as a combination of the two networks and network load between the effects negligible. The first network equivalent to a sub-circuit pressure circuit. When either from RLminRlmax, it takes a change in sexual Jieyue, UA as a given the Jieyue signal. UA (t) =Rlmax/ (Rlmax+R0) U t=0 UA (t) =Rlmin/ (Rlmin+R0) U t0 Jieyue use this signal as the second circuit network, a band differential input circuits may be under Type : (d/dt) UA (t) = (1/RC) URST (t) + (d/dt) URST (t) URST (0) 0From style can be seen as the load voltage of the power supply voltage change and the role in the introduction of a category of spaces - pulse, leading to abnormal CPU work. 1.2 scoring type of spaces circuit The circuit equivalent circuit shown in figure 5. Still Gaodianping restoration, for example, can establish the following equation : When the system call, assumptions upon Us (t) =AU (t) Jieyue function, U0=0 when Fanxiang devices normal work, if Uz remain in the Vil, the output can be thought Gaodianping; And if from the start after normal work Fanxiang devices, after not less than resetting pulse width time TR, Uz can reach Vil above, then, the spaces will be able to ensure reliable electricity. So in practical applications, designers often R, CF increased to enhance the value of time constants, and the application of CMOS Fanxiang Simite imported vehicles to enhance anti-interference. However this restoration circuit switching often in a relatively short time power intervals unusual circumstances. This was mainly due to discharge circuit with the same charging circuit, leading to greater discharge time constants, leading to UC excessive voltage drop.Discharge circuit can be seen far less than the time constants general charging time constants. Then, the above-mentioned duplication resulting from the switching power supply unreliable electricity restoration phenomenon can be controlled. However, the discharge time constants too short reduces the restoration work on the circuit in the power supply voltage fluctuations are not sensitive. For example, when power supply voltage fluctuations, at the discharge quickly, thereby making it possible to create Uz below Fanxiang devices Vil voltage value, unnecessary restoration pulse. This phenomenon in Single-chip microcomputer work in Sleep mode and enabling manner cut over, and power is relatively weak output may arise. Move to improve the integration of the above phenomena of spaces circuit, R1R2, appropriate adjustments can avoid Steven value size above happen.13 more spaces by type of circuit , call the spaces, because the formation of a RC low-network, so that more vehicles are being imported - voltage than the negative-input voltage of the delay time. Compared with the negative side of the network time constants are much smaller than the ends of the RC time constants networks, and in-voltage is also no more than a negative-voltage, compared with export Didianping by Fanxiang device after a Gaodianping. Restoration of normal voltage pulse width depends mainly on the rising rate. The negative-voltage discharge circuit time constants larger, and therefore not sensitive to fluctuations in the power supply voltage. However prone to the following two kinds of adverse phenomena : (1) spacing too short supply two switches, the spaces are not reliable; (2) When the power supply voltage is blowing phenomenon, might not have gone in front of spaces pulse. This will be more highly regarded for improving the circuit. This circuit can be improved to eliminate the phenomenon of the first and second reduction phenomena. To remove the two types of phenomena, we can use the methods and digital logic devices with more and more highly regarded for circuit design. This circuit can be slightly improved as a watchdog on power restoration and the restoration of common spaces circuit circuit, greatly improving the reliability of spaces.1.4 man-resetting circuit Man-restoration circuits mainly use CPU normal work, regularly resetting counter, the value of which does not exceed a certain value rod; When the CPU is not normal work, not quite as counter spaces, the number will exceed a certain value, therefore, resulting in the spaces pulse, making CPU restore normal working conditions. This depends primarily on the reliability of spaces circuit design software to be sent regularly to restore circuit pulse procedure placement. General design, this procedure will be placed on digital library service interruption. However, sometimes such a design will work or not to fly away from the normal procedures. The main reason is : When procedures to fly and the interruption occurs timer substantially after, the walk around of the situation could not be rectified spaces circuit back. As a real disruption in a timer, even if the procedure is not normal, but also to be normal spaces. Move timer plus pre-set design. In a substantially when pressed into Duizhan address, the address in this implementation is a cycle of disruption and a death sentence. In all procedures code was not occupied by preserving as much as possible the return address instructions rep replaced. Thus, when the procedure to fly, the possibility of its entry into traps will be greatly increased. Once entered traps timer stop work and the closure of interruption, thereby & restoration circuit will have a pulse of the place of the CPU spaces. Of course, such technology for real-time processing software, strong control or have some difficulties. 2 dedicated chips on the spaces (MAX813L) Currently, there are many popular in the market place for the chip, understand their operating principles of circuit reliability analysis and design is essential. MAX813L voice to the production company, for example, dissecting the spaces dedicated to the general operating principles of chips. For other chips, according to statistics provided by four of its 11 members circuit analysis can seek conclusions. MAX813L with the call of spaces, & export, Diaodian voltage surveillance, manual functions of the four spaces. Specific principles diagram shown in figure 12. The discussion of spaces limited to circuit and watchdog timer component parts. WDI (& Input) mainly as a replacement for & register. If the CPU is not in 1.6 seconds trigger restoration watchdog timer, WDO (& Output) will export Didianping. Manual resetting circuit consists of spaces with electricity restoration. As can be seen from the principles of 12, with the restoration of electricity referred circuit this same principle, namely, a device used to trigger a signal trigger capability to produce restore signals. At the same time, based on the pulse of a set, when the time to 140 milliseconds spaces, Reset generator to produce a pulse of spaces signal invalid. , call the spaces, as long as voltage below 4.63V, Reset signal of spaces on effective; When the power supply voltage exceeds 4.63V, Reset signal will remain at about 140 milliseconds, to ensure reliable CPU restoration after invalid. Manual restoration, displays (Manual Reset) grounded time not less than 150 airborne, they can produce a manual restoration process. In a 140-millisecond restoration of the effective restoration signals (Gaodianping effective). If WDO-linking with displays may call for the composition of spaces and the spaces circuit criminals. 3 attention of spaces circuit design point All of the spaces mentioned circuit, differentiation of spaces circuit simple, but not easy to interfere with the ability to monitor CPU operation; Bonus Point restoration circuit simple and reliable, but is not sensitive to fluctuations due to supply voltage, thus likely to be CPU and the power supply voltage caused by the work of an abnormal low; Comparison with the more complex spaces circuit circuit, Working reliable ;Watchdog restoration circuit circuit more complex, reliable and have the ability to monitor CPU operation. In the use of space should be based on the circuit board, power supply voltage characteristics, such as on-site operation of the system, integrated into the case. As the following articles for reference : (1) Type of spaces in the use of differential voltage power circuit and use should be considered when appropriate in the inductance - capacitance input to reduce load mutations caused by the interference of spaces pulse. In the limited space of circuit boards can choose to place this circuit. (2) the use of spaces - scoring circuit, on the other hand, should be given to electricity supply voltage of spaces, the increased rate, particularly in the smaller power voltage rise rates should be consider