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单片机英文文献资料及翻译单片机(英文：Microcontroller)Microcontroller is a small computer on a single integrated circuit that contains a processor core, memory, and programmable input/output peripherals. Microcontrollers are designed for embedded applications, in contrast to the microprocessors used in personal computers or other general purpose applications.A microcontroller's processor core is typically a small, low-power computer dedicated to controlling the operation of the device in which it is embedded. It is often designed to provide efficient and reliable control of simple and repetitive tasks, such as switching on and off lights, or monitoring temperature or pressure sensors.MEMORYMicrocontrollers typically have a limited amount of memory, divided into program memory and data memory. The program memory is where the software that controls the device is stored, and is often a type of Read-Only Memory (ROM). The data memory, on the other hand, is used to store data that is used by the program, and is often volatile, meaning that it loses its contents when power is removed.INPUT/OUTPUTMicrocontrollers typically have a number of programmable input/output (I/O) pins that can be used to interface with external sensors, switches, actuators, and other devices. These pins can be programmed to perform specific functions,such as reading a sensor value, controlling a motor, or generating a signal. Many microcontrollers also support communication protocols like serial, parallel, and USB, allowing them to interface with other devices, including other microcontrollers, computers, and smartphones.APPLICATIONSMicrocontrollers are widely used in a variety of applications, including:- Home automation systems- Automotive electronics- Medical devices- Industrial control systems- Consumer electronics- RoboticsCONCLUSIONIn conclusion, microcontrollers are powerful and versatile devices that have become an essential component in many embedded systems. With their small size, low power consumption, and high level of integration, microcontrollers offer an effective and cost-efficient solution for controlling a wide range of devices and applications.。
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Validation and Testing of Design Hardening for Single Event Effects Using the 8051 MicrocontrollerAbstractWith the dearth of dedicated radiation hardened foundries, new and novel techniques are being developed for hardening designs using non-dedicated foundry services. In this paper, we will discuss the implications of validating these methods for the single event effects (SEE) in the space environment. Topics include the types of tests that are required and the design coverage (i.e., design libraries: do they need validating for each application?). Finally, an 8051 microcontroller core from NASA Institute of Advanced Microelectronics (IAμE) CMOS Ultra Low Power Radiation Tolerant (CULPRiT) design is evaluated for SEE mitigative techniques against two commercial 8051 devices.Index TermsSingle Event Effects, Hardened-By-Design, microcontroller, radiation effects.I. INTRODUCTIONNASA constantly strives to provide the best capture of science while operating in a space radiation environment using a minimum of resources [1,2]. With a relatively limited selection of radiation-hardened microelectronic devices that are often two or more generations of performance behind commercialstate-ofthe-art technologies, NASA’s performance of this task is quite challenging. One method of alleviating this is by the use of commercial foundry alternatives with no or minimally invasive design techniques for hardening. This is often called hardened-by-design (HBD).Building custom-type HBD devices using design libraries and automated design tools may provide NASA the solution it needs to meet stringent science performance specifications in a timely,cost-effective, and reliable manner.However, one question still exists: traditional radiation-hardened devices have lot and/or wafer radiation qualification tests performed; what types of tests are required for HBD validation?II. TESTING HBD DEVICES CONSIDERATIONSTest methodologies in the United States exist to qualify individual devices through standards and organizations such as ASTM, JEDEC, and MIL-STD- 883. Typically, TID (Co-60) and SEE (heavy ion and/or proton) are required for device validation. So what is unique to HBD devices?As opposed to a “regular” commercial-off-the-shelf (COTS) device or application specific integrated circuit (ASIC) where no hardening has been performed, one needs to determine how validated is the design library as opposed to determining the device hardness. That is, by using test chips, can we “qualify” a future device using the same library?Consider if Vendor A has designed a new HBD library portable to foundries B and C. A test chip is designed, tested, and deemed acceptable. Nine months later a NASA flight project enters the mix by designing a new device using Vendor A’s library. Does this device require complete radiation qualification testing? To answer this, other questions must be asked.How complete was the test chip? Was there sufficient statistical coverage of all library elements to validate each cell? If the new NASA design uses a partially or insufficiently characterized portion of the design library, full testing might be required. Of course, if part of the HBD was relying on inherent radiation hardness of a process, some of the tests (like SEL in the earlier example) may be waived.Other considerations include speed of operation and operating voltage. For example, if the test chip was tested statically for SEE at a power supply voltage of 3.3V, is the data applicable to a 100 MHz operating frequency at 2.5V? Dynamic considerations (i.e., nonstatic operation) include the propagated effects of Single Event Transients (SETs). These can be a greater concern at higher frequencies.The point of the considerations is that the design library must be known, the coverage used during testing is known, the test application must be thoroughly understood and the characteristics of the foundry must be known. If all these are applicable or have been validated by the test chip, then no testing may be necessary. A task within NASA’s Electronic Parts and Packaging (NEPP) Program was performed to explore these types of considerations.III. HBD TECHNOLOGY EVALUATION USING THE 8051 MICROCONTROLLERWith their increasing capabilities and lower power consumption, microcontrollers are increasingly being used in NASA and DOD system designs. There are existing NASA and DoD programs that are doing technology development to provide HBD. Microcontrollers are one such vehicle that is being investigated to quantify the radiation hardness improvement. Examples of these programs are the 8051 microcontroller being developed by Mission Research Corporation (MRC) and the IAμE (the focus of this study). As these HBD technologies become available, validation of the technology, in the natural space radiation environment, for NASA’s use in spaceflight systems is required.The 8051 microcontroller is an industry standard architecture that has broad acceptance, wide-ranging applications and development tools available. There are numerous commercial vendors that supply this controller or have it integrated into some type of system-on-a-chip structure. Both MRC and IAμE chose this device to demonstrate two distinctly different technologies for hardening. The MRC example of this is to use temporal latches that require specific timing to ensure that single event effects are minimized. The IAμE technology uses ultra low power, and layout and architecture HBD design rules to achieve their results. These are fundamentally different than the approach by Aeroflex-United Technologies Microelectronics Center (UTMC), the commercial vendor of a radiation–hardened 8051, that built their 8051 microcontroller using radiationhardened processes. This broad range of technology within one device structure makes the 8051an ideal vehicle for performing this technology evaluation.The objective of this work is the technology evaluation of the CULPRiT process [3] from IAμE. The process has been baselined against two other processes, the standard 8051 commercial device from Intel and a version using state-of-the-art processing from Dallas Semiconductor. By performing this side-by-side comparison, the cost benefit, performance, and reliability trade study can be done.In the performance of the technology evaluation, this task developed hardware and software for testing microcontrollers. A thorough process was done to optimize the test process to obtain as complete an evaluation as possible. This included taking advantage of the available hardware and writing software that exercised the microcontroller such that all substructures of the processor were evaluated. This process is also leading to a more complete understanding of how to test complex structures, such as microcontrollers, and how to more efficiently test these structures in the future.IV. TEST DEVICESThree devices were used in this test evaluation. The first is the NASA CULPRiT device, which is the primary device to be evaluated. The other two devices are two versions of a commercial 8051, manufactured by Intel and Dallas Semiconductor, respectively.The Intel devices are the ROMless, CMOS version of the classic 8052 MCS-51 microcontroller. They are rated for operation at +5V, over a temperature range of 0 to 70 °C and at a clock speeds of 3.5 MHz to 24 MHz. They are manufactured in Intel’s P629.0 CHMOS III-E process.The Dallas Semiconductor devices are similar in that they are ROMless 8052 microcontrollers, but they are enhanced in various ways. They are rated for operation from 4.25 to 5.5 Volts over 0 to 70 °C at clock speeds up to 25 MHz. They have a second full serial port built in, seven additional interrupts, a watchdog timer, a power fail reset, dual data pointers and variable speed peripheral access. In addition, the core is redesigned so that the machine cycle is shortened for most instructions, resulting in an effective processing ability that is roughly 2.5 times greater (faster) than the standard 8052 device. None of these features, other than those inherent in the device operation, were utilized in order to maximize the similarity between the Dallas and Intel test codes.The CULPRiT technology device is a version of the MSC-51 family compatible C8051 HDL core licensed from the Ultra Low Power (ULP) process foundry. The CULPRiT technology C8051 device is designed to operate at a supply voltage of 500 mV and includes an on-chip input/output signal level-shifting interface with conventional higher voltage parts. The CULPRiT C8051 device requires two separate supply voltages; the 500 mV and the desired interface voltage. The CULPRiT C8051 is ROMless and is intended to be instruction set compatible with the MSC-51 family.V. TEST HARDWAREThe 8051 Device Under Test (DUT) was tested as a component of a functional computer. Aside from DUT itself, the other componentsof the DUT computer were removed from the immediate area of the irradiation beam.A small card (one per DUT package type) with a unique hard-wired identifier byte contained the DUT, its crystal, and bypass capacitors (and voltage level shifters for the CULPRiT DUTs). This "DUT Board" was connected to the "Main Board" by a short 60-conductor ribbon cable. The Main Board had all other components required to complete the DUT Computer, including some which nominally are not necessary in some designs (such as external RAM, external ROM and address latch). The DUT Computer and the Test Control Computer were connected via a serial cable and communications were established between the two by the Controller (that runs custom designed serial interface software). This Controller software allowed for commanding of the DUT, downloading DUT Code to the DUT, and real-time error collection from the DUT during and post irradiation. A 1 Hz signal source provided an external watchdog timing signal to the DUT, whose watchdog output was monitored via an oscilloscope. The power supply was monitored to provide indication of latchup.VI. TEST SOFTWAREThe 8051 test software concept is straightforward. It was designed to be a modular series of small test programs each exercising a specific part of the DUT. Since each test was stand alone, they were loaded independently of each other for execution on the DUT. This ensured that only the desired portion of the 8051 DUT was exercised during the test and helped pinpoint location of errors that occur during testing. All test programs resided on the controller PC until loaded via the serial interface to the DUT computer. In this way, individual tests could have been modified at any time without the necessity of burning PROMs. Additional tests could have also been developed and added without impacting the overall test design. The only permanent code, which was resident on the DUT, was the boot code and serial code loader routines that established communications between the controller PC and the DUT.All test programs implemented:• An external Universal Asynchronous Receive and Transmit device (UART) for transmission of error information and communication to controller computer.• An external real-time clock for data error tag.•A watchdog routine designed to provide visual verification of 8051 health and restart test code if necessary.• A "foul-up" routine to reset program counter if it wanders out of code space.• An external telemetry data storage memory to provide backup of data in the event of an interruption in data transmission.The brief description of each of the software tests used is given below. It should be noted that for each test, the returned telemetry (including time tag) was sent to both the test controller and the telemetry memory, giving the highest reliability that all data is captured.Interrupt –This test used 4 of 6 available interrupt vectors (Serial, External, Timer0 Overflow, and Timer1 Overflow) to trigger routines that sequentially modified a value in the accumulator which was periodically compared to a known value. Unexpected values were transmitted with register information.Logic –This test performed a series of logic and math computations and provided three types of error identifications: 1) addition/subtraction, 2) logic and 3) multiplication/division. All miscompares of computations and expected results were transmitted with other relevant register information.Memory – This test loaded internal data memory at locations D:0x20 through D:0xff (or D:0x20 through D:0x080 for the CULPRiT DUT), indirectly, with an 0x55 pattern. Compares were performed continuously and miscompares were corrected while error information and register values were transmitted.Program Counter -The program counter was used to continuously fetch constants at various offsets in the code. Constants were compared with known values and miscompares were transmitted along with relevant register information. Registers – This test loaded each of four (0,1,2,3) banks of general-purpose registers with either 0xAA (for banks 0 and 2) or 0x55 (for banks 1 and 3). The pattern was alternated in order to test the Program Status Word (PSW) special function register, which controls general-purpose register bank selection. General-purpose register banks were then compared with their expected values. All miscompares were corrected and error information was transmitted.Special Function Registers (SFR) – This test used learned static values of 12 out 21 available SFRs and then constantly compared the learned value with the current one. Miscompares were reloaded with learned value and error information was transmitted.Stack – This test performed arithmetic by pushing and popping operands on the stack. Unexpected results were attributed to errors on the stack or to the stack pointer itself and were transmitted with relevant register information.VII. TEST METHODOLOGYThe DUT Computer booted by executing the instruction code located at address 0x0000. Initially, the device at this location was an EPROM previously loaded with "Boot/Serial Loader" code. This code initialized the DUT Computer and interface through a serial connection to the controlling computer, the "Test Controller". The DUT Computer downloaded Test Code and put it into Program Code RAM (located on the Main Board of the DUT Computer). It then activated a circuit which simultaneously performed two functions: held the DUT reset line active for some time (~10 ms); and, remapped the Test Code residing in the Program Code RAM to locate it to address 0x0000 (the EPROM will no longer be accessible in the DUT Computer's memory space). Upon awaking from the reset, the DUT computer again booted by executing the instruction code at address 0x0000, except this time that code was not be the Boot/Serial Loader code but the Test Code.The Test Control Computer always retained the ability to force the reset/remap function, regardless of the DUT Computer's functionality. Thus, if the test ran without a Single Event Functional Interrupt (SEFI) either the DUT Computer itselfor the Test Controller could have terminated the test and allowed the post-test functions to be executed. If a SEFI occurred, the Test Controller forced a reboot into Boot/Serial Loader code and then executed the post-test functions. During any test of the DUT, the DUT exercised a portion of its functionality (e.g., Register operations or Internal RAM check, or Timer operations) at the highest utilization possible, while making a minimal periodic report to the Test Control Computer to convey that the DUT Computer was still functional. If this reportceased, the Test Controller knew that a SEFI had occurred. This periodic data was called "telemetry". If the DUT encountered an error that was not interrupting the functionality (e.g., a data register miscompare) it sent a more lengthy report through the serial port describing that error, and continued with the test.VIII.DISCUSSIONA. Single Event LatchupThe main argument for why latchup is not an issue for the CULPRiT devices is that the operating voltage of 0.5 volts should be below the holding voltage required for latchup to occur. In addition to this, the cell library used also incorporates the heavy dual guard-barring scheme [4]. This scheme has been demonstrated multiple times to be very effective in rendering CMOS circuits completely immune to SEL up to test limits of 120 MeV-cm2/mg. This is true in circuits operating at 5, 3.3, and 2.5 Volts, as well as the 0.5 Volt CULPRiT circuits. In one case, a 5 Volt circuit fabricated on noncircuits wafers even exhibited such SEL immunity.B. Single Event UpsetThe primary structure of the storage unit used in the CULPRiT devices is the Single Event Resistant Topology (SERT) [5]. Given the SERT cell topology and a single upset node assumption, it is expected that the SERT cell will be completely immune to SEUs occurring internal to the memory cell itself. Obviously there are other things going on. The CULPRiT 8051 results reported here are quite similar to some resultsobtained with a CULPRiT CCSDS lossless compression chip (USES) [6]. The CULPRiT USES was synthesized using exactly the same tools and library as the CULPRiT 8051.With the CULPRiT USES, the SEU cross section data [7] was taken as a function of frequency at two LET values, 37.6 and 58.5 MeV-cm2/mg. In both cases the data fit well to a linear model where cross section is proportional to clock. In the LET 37.6 case, the zero frequency intercept occurred essentially at the zero cross section point, indicating that virtually all of these SEUs are captured SETs from the combinational logic. The LET 58.5 data indicated that the SET (frequency dependent) component is sitting on top of a "dc-bias" component –presumably a second upset mechanism is occurring internal to the SERT cells only at a second, higher LET threshold.The SET mitigation scheme used in the CULPRiT devices is based on the SERT cell's fault tolerant input property when redundant input data is provided to separate storage nodes. The idea is that the redundant input data is provided through a total duplication of combinational logic (referred to as “dual rail design”) such that a simple SET on one rail cannot produce an upset. Therefore, some other upset mechanism must be happening. It is possible that a single particle strike is placing an SET on both halves of the logic streams, allowing an SET to produce an upset. Care was taken to separate the dual sensitive nodes in the SERT cell layouts but the automated place-and-route of the combinatorial logic paths may have placed dual sensitive nodes close enough.At this point, the theory for the CULPRiT SEU response is that at about an LET of 20, the energy deposition is sufficiently wide enough (and in the right locations) to produce an SET in both halves of the combinatorial logic streams. Increasing LET allows for more regions to be sensitive to this effect, yielding a larger cross section. Further, the second SEU mechanism that starts at an LET of about 40-60 has to do with when the charge collection disturbance cloud gets large enough to effectively upset multiples of the redundant storage nodes within the SERT cell itself. In this 0.35 μm library, the node separation is several microns. However, since it takes less charge to upset a node operating at 0.5 Volts, with transistors having effective thresholds around 70 mV, this is likely the effect being observed. Also the fact that the per-bit memory upset cross section for the CULPRiT devices and the commercial technologies are approximately equal, as shown in Figure 9, indicates that the cell itself has become sensitive to upset.IX. SUMMARYA detailed comparison of the SEE sensitivity of a HBD technology (CULPRiT) utilizing the 8051 microcontroller as a test vehicle has been completed. This paper discusses the test methodology used and presents a comparison of the commercial versus CULPRiT technologies based on the data taken. The CULPRiT devices consistently show significantly higher threshold LETs and an immunity to latchup. In all but the memory test at the highest LETs, the cross section curves for all upset events is one to two orders of magnitude lower than the commercial devices. Additionally, theory is presented, based on the CULPRiT technology, that explain these results.This paper also demonstrates the test methodology for quantifying the level of hardness designed into a HBD technology. By using the HBD technology in a real-world device structure (i.e., not just a test chip), and comparing results to equivalent commercial devices, one can have confidence in the level of hardness that would be available from that HBD technology in any circuit application.ACKNOWLEDGEMENTSThe authors of this paper would like to acknowledge the sponsors of this work. These are the NASA Electronic Parts and Packaging Program (NEPP), NASA Flight Programs, and the Defense Threat Reduction Agency (DTRA).。
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ABOUT SCMIt can be said across the twentieth century, the three "electric" era, that is, electrical era, the electronic age, and has now entered the computer age. However, such a computer, usually refers to the personal computer, referred to as PC. It consists of the host, keyboard, monitor etc.. Another type of computer, most people do not know how. This computer is to smart to give a variety of mechanical microcontroller (also known as micro-controller). As the name suggests, this computer system only used the smallest one IC, you can perform simple operations and control. Because of its small size, usually hidden in a charged mechanical "stomach" Lane. It is the entire device, like the human brain plays a role, it goes wrong, the whole device was paralyzed.Now, this MCU has a very wide field of use, such as smart meters, real-time industrial control, communications equipment, navigation systems, home appliances and so on. Once the microcontroller were using a variety of products, you can serve to upgrade the effectiveness of the product, often in the product name is preceded by the adjective - "smart", such as washing machines and so intelligent. At present, some technical personnel of factories or other amateur electronics developers to engage in out of certain products, not the circuit is too complex, that is, functions are too simple and easy to be copied. The reason may be stuck in the product without the use of a microcontroller or other programmable logic device.SCM basic component is a central processing unit (CPU in the computing device and controller), read-only memory (usually expressed as a ROM), read-write memory (also known as Random Access Memory MRAM is usually expressed as a RAM) , input / output port (also divided into parallel port and serial port, expressed as I / O port), and so composed. In fact there is also a clock circuit microcontroller, so that during operation and control of the microcontroller, can rhythmic manner. In addition, there are so-called "break system", the system is a "janitor" role, when the microcontroller control object parameters that need to be intervention to reach a particular state, can after this "janitor" communicated to the CPU, so that CPU priorities of the external events to take appropriate counter-measures.Electric boiler temperature system1.MCUA microcontroller (or MCU) is a computer-on-a-chip. It is a type of microprocessor emphasizing self-sufficiency and cost-effectiveness, in contrast to a general-purpose microprocessor (the kind used in a PC).The majority of computer systems in use today are embedded in other machinery, such as telephones, clocks, appliances, vehicles, and infrastructure. An embedded system usually has minimal requirements for memory and program length and may require simple but unusual input/output systems. For example, most embedded systems lack keyboards, screens, disks, printers, or other recognizable I/O devices of a personal computer. They may control electric motors, relays or voltages, and read switches, variable resistors or other electronic devices. Often, the only I/O device readable by a human is a single light-emitting diode, and severe cost or power constraints can even eliminate that.In contrast to general-purpose CPUs, microcontrollers do not have an address bus or a data bus, because they integrate all the RAM and non-volatile memory on the same chip as the CPU. Because they need fewer pins, the chip can be placed in a much smaller, cheaper package.Integrating the memory and other peripherals on a single chip and testing them as a unit increases the cost of that chip, but often results in decreased net cost of the embedded system as a whole. (Even if the cost of a CPU that has integrated peripherals is slightly more than the cost of a CPU + external peripherals, having fewer chips typically allows a smaller and cheaper circuit board, and reduces the labor required to assemble and test the circuit board). This trend leads to design.A microcontroller is a single integrated circuit, commonly with the following features: central processing unit - ranging from small and simple 4-bit processors to sophisticated32- or 64-bit processorsinput/output interfaces such as serial ports (UARTs)other serial communications interfaces like I²C, Serial Peripheral Interface and Controller Area Network for system interconnect peripherals such as timers and watchdog RAM for data storage ROM, EPROM, EEPROM or Flash memory for program storage clock generator - often an oscillator for a quartz timing crystal, resonator or RC circuit many include analog-to-digital converters .This integration drastically reduces the number of chips and the amount of wiring and PCB space that would be needed to produce equivalent systems using separate chips and have proved to be highly popular in embedded systems since their introduction in the 1970s.Some microcontrollers can afford to use a Harvard architecture: separate memory buses for instructions and data, allowing accesses to take place concurrently.The decision of which peripheral to integrate is often difficult. The Microcontroller vendors often trade operating frequencies and system design flexibility against time-to-market requirements from their customers and overall lower system cost. Manufacturers have to balance the need to minimize the chip size against additional functionality.Microcontroller architectures are available from many different vendors in so many varieties that each instruction set architecture could rightly belong to a category of their own. Chief among these are the 8051, Z80 and ARM derivatives.[citation needed]A microcontroller (also MCU or µC) is a functional computer system-on-a-chip. It contains a processor core, memory, and programmable input/output peripherals. Microcontrollers include an integrated CPU, memory (a small amount of RAM, program memory, or both) and peripherals capable of input and output.It emphasizes high integration, in contrast to a microprocessor which only contains a CPU (the kind used in a PC). In addition to the usual arithmetic and logic elements of a general purpose microprocessor, the microcontroller integrates additional elements such as read-write memory for data storage, read-only memory for program storage, Flash memory for permanent data storage, peripherals, and input/output interfaces. At clock speeds of as little as 32KHz, microcontrollers often operate at very low speed compared to microprocessors, but this is adequate for typical applications. They consume relatively little power (milliwatts or even microwatts), and will generally have the ability to retain functionality while waiting for an event such as a button press or interrupt. Power consumption while sleeping (CPU clock and peripherals disabled) may be just nanowatts, making them ideal for low power and long lasting battery applications.Microcontrollers are used in automatically controlled products and devices, such as automobile engine control systems, remote controls, office machines, appliances, power tools, and toys. By reducing the size, cost, and power consumption compared to a design using a separate microprocessor, memory, and input/output devices, microcontrollers make it economical to electronically control many more processes.The majority of computer systems in use today are embedded in other machinery, such as automobiles, telephones, appliances, and peripherals for computer systems. These are called embedded systems. While some embedded systems are very sophisticated, many have minimal requirements for memory and program length, with no operating system, and low software complexity. Typical input and output devices include switches, relays, solenoids, LEDs, small or custom LCD displays, radio frequency devices, and sensors for data such as temperature, humidity, light level etc. Embedded systems usually have no keyboard, screen, disks, printers, or other recognizable I/O devices of a personal computer, and may lack human interaction devices of any kind.It is mandatory that microcontrollers provide real time response to events in the embedded system they are controlling. When certain events occur, an interrupt system can signal the processor to suspend processing the current instruction sequence and tobegin an interrupt service routine (ISR). The ISR will perform any processing required based on the source of the interrupt before returning to the original instruction sequence. Possible interrupt sources are device dependent, and often include events such as an internal timer overflow, completing an analog to digital conversion, a logic level change on an input such as from a button being pressed, and data received on a communication link. Where power consumption is important as in battery operated devices, interrupts may also wake a microcontroller from a low power sleep state where the processor is halted until required to do something by a peripheral event.Microcontroller programs must fit in the available on-chip program memory, since it would be costly to provide a system with external, expandable, memory. Compilers and assembly language are used to turn high-level language programs into a compact machine code for storage in the microcontroller's memory. Depending on the device, the program memory may be permanent, read-only memory that can only be programmed at the factory, or program memory may be field-alterable flash or erasable read-only memory.Since embedded processors are usually used to control devices, they sometimes need to accept input from the device they are controlling. This is the purpose of the analog to digital converter. Since processors are built to interpret and process digital data, i.e. 1s and 0s, they won't be able to do anything with the analog signals that may be being sent to it by a device. So the analog to digital converter is used to convert the incoming data into a form that the processor can recognize. There is also a digital to analog converter that allows the processor to send data to the device it is controlling.In addition to the converters, many embedded microprocessors include a variety of timers as well. One of the most common types of timers is the Programmable Interval Timer, or PIT for short. A PIT just counts down from some value to zero. Once it reaches zero, it sends an interrupt to the processor indicating that it has finished counting. This is useful for devices such as thermostats, which periodically test the temperature aroundthem to see if they need to turn the air conditioner on, the heater on, etc.Time Processing Unit or TPU for short. Is essentially just another timer, but more sophisticated. In addition to counting down, the TPU can detect input events, generate output events, and other useful operations.Dedicated Pulse Width Modulation (PWM) block makes it possible for the CPU to control power converters, resistive loads, motors, etc., without using lots of CPU resources in tight timer loops.Universal Asynchronous Receiver/Transmitter (UART) block makes it possible to receive and transmit data over a serial line with very little load on the CPU.For those wanting ethernet one can use an external chip like Crystal Semiconductor CS8900A, Realtek RTL8019, or Microchip ENC 28J60. All of them allow easy interfacing with low pin count.。
单片机英文资料英文文献
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.s0791 eht ni noi tcudortni rieht ecnis smetsys deddebme ni ralupop ylhgih eb ot devorp evah dna spihc etarapes gnisu smetsys tnelaviuqe ecudorp ot dedeen eb dluow taht ecaps BCP dna gniriw fo tnuoma eht dna spihc fo rebmun eht secuder yllaci tsard noitargetni sihT sretrevnoc latigid-ot-golana edulcni ynam tiucric CR ro rotanoser ,latsyrc gnimit ztrauq a rof rotallicso na netfo - rotareneg kcolc egarots margorp rof yromem hsalF ro MORPEE ,MORPE ,MOR egarots atad rof MAR godhctaw dna sremi t sa hcus slarehpirep tcennocretni metsys rof krowteN aerA rellortnoC dna ecafretnI larehpireP laireS ,C²I ekil secafretni snoi tacinumm oc laires rehto )sTRAU( strop laires sa hcus secafretni tuptuo/tupni srossecorp tib-46 ro -23 detaci tsihpos ot srossecorp tib-4 elpmis dna llams m orf gnignar - tinu gnissecorp lartnec :serutaef gniwoll of eht h tiw yln ommoc ,tiucric detargetni elgnis a si rellortnocorcim A .ngised ot sdael dnert sihT .)draob tiucric eht tset dna elbmessa ot deriuqer robal eht secuder dna ,draob tiucric repaehc dna rell ams a swolla yllacipyt spihc rewef gnivah ,slarehpirep lanretxe + UPC a fo tsoc eht naht erom ylthgils si slarehpirep detargetni sah taht UPC a fo tsoc eht fi nevE( .el ohw a sa metsys deddebme eht fo tsoc ten desaerced ni stluser netfo tub ,pihc taht fo ts oc eht sesaercni tinu a sa meht gnitset dna pihc elgnis a no slarehpirep rehto dna yromem eht gnitargetnI .egakcap repaehc ,rellams hcum a ni decalp eb nac pihc eht ,snip rewef deen yeht esuaceB .UPC eht sa pihc emas eht no yromem elital ov-non dna MAR eh t lla etargetni yeht esuaceb ,sub atad a ro sub sserdda na evah ton od srellortnocorcim ,sUPC esoprup-lareneg ot tsartnoc nI .taht etanimile neve nac stniartsnoc rewop ro tsoc ereves dna ,edoid gni ttime- thgil elgnis a si namuh a yb elbadaer ecived O/I yl no eht ,netfO .secived cinortcele rehto ro srotsiser elbairav ,sehctiws daer dna ,segatlov ro syaler ,srotom cirtcele lortnoc yam yehT .retupm oc lanosrep a fo secived O/I elbazingocer rehto ro ,sretnirp ,sksid ,sneercs ,sdraobyek kcal smetsys deddebme tsom ,elpmaxe roF .smetsys tuptuo/tupni lausunu tub elpmis eriuqer yam dna htgnel margorp dna yromem rof stnemeriuqer laminim sah yllausu metsys deddebme nA .erutcurtsarfni dna ,selcihev ,secnailppa ,skcolc ,senohpelet sa hcus ,yrenihcam rehto ni deddebme era yadot esu ni smetsys retupmoc f o y tirojam ehT .)CP a ni desu dnik eht( rossecorporcim esoprup-lareneg a ot tsartnoc ni ,ssenevi tceffe-tsoc dna ycneiciffus-fles gnizisahpme rossecorporcim fo epyt a si tI .pihc-a-no- retupmoc a si )UCM ro( rellortnocorcim A
单片机英文参考文献
单片机英文参考文献篇一：5-单片机+外文文献+英文文献+外文翻译中英对照AT89C51的介绍（原文出处：http：///resource/）描述AT89C51是一个低电压，高性能CMOS8位单片机带有4K字节的可反复擦写的程序存储器（PENROM）。
和128字节的存取数据存储器（RAM），这种器件采用ATMEL公司的高密度、不容易丢失存储技术生产，并且能够与MCS-51系列的单片机兼容。
片内含有8位中央处理器和闪烁存储单元，有较强的功能的AT89C51单片机能够被应用到控制领域中。
功能特性AT89C51提供以下的功能标准：4K字节闪烁存储器，128字节随机存取数据存储器，32个I/O口，2个16位定时/计数器，1个5向量两级中断结构，1个串行通信口，片内震荡器和时钟电路。
另外，AT89C51还可以进行0HZ的静态逻辑操作，并支持两种软件的节电模式。
闲散方式停止中央处理器的工作，能够允许随机存取数据存储器、定时/计数器、串行通信口及中断系统继续工作。
掉电方式保存随机存取数据存储器中的内容，但震荡器停止工作并禁止其它所有部件的工作直到下一个复位。
引脚描述VCC：电源电压 GND：地 P0口：P0口是一组8位漏极开路双向I/O口，即地址/数据总线复用口。
作为输出口时，每一个管脚都能够驱动8个TTL电路。
当“1”被写入P0口时，每个管脚都能够作为高阻抗输入端。
P0口还能够在访问外部数据存储器或程序存储器时，转换地址和数据总线复用，并在这时激活内部的上拉电阻。
P0口在闪烁编程时，P0口接收指令，在程序校验时，输出指令，需要接电阻。
沈阳航空工业学院电子工程系毕业设计（外文翻译）P1口：P1口一个带内部上拉电阻的8位双向I/O口，P1的输出缓冲级可驱动4个TTL电路。
对端口写“1”，通过内部的电阻把端口拉到高电平，此时可作为输入口。
因为内部有电阻，某个引脚被外部信号拉低时输出一个电流。
闪烁编程时和程序校验时，P1口接收低8位地址。
单片机外文文献
Microcomputer SystemsElectronic systems are used for handing information in the most general sense; this information may be telephone conversation, instrument read or a company’s accounts, but in each case the same main type of operation are involved: the processing, storage and transmission of information. in conventional electronic design these operations are combined at the function level; for example a counter, whether electronic or mechanical, stores the current and increments it by one as required. A system such as an electronic clock which employs counters has its storage and processing capabilities spread throughout the system because each counter is able to store and process numbers.Present day microprocessor based systems depart from this conventional approach by separating the three functions of processing, storage, and transmission into different section of the system. This partitioning into three main functions was devised by V on Neumann during the 1940s, and was not conceived especially for microcomputers. Almost every computer ever made has been designed with this structure, and despite the enormous range in their physical forms, they have all been of essentially the same basic design.In a microprocessor based system the processing will be performed in the microprocessor itself. The storage will be by means of memory circuits and the communication of information into and out of the system will be by means of special input/output(I/O) circuits. It would be impossible to identify a particular piece of hardware which performed the counting in a microprocessor based clock because the time would be stored in the memory and incremented at regular intervals but the microprocessor. However, the software which defined the system’s behavior woul d contain sections that performed as counters. The apparently rather abstract approach to the architecture of the microprocessor and its associated circuits allows it to be very flexible in use, since the system is defined almost entirely software. The design process is largely one of software engineering, and the similar problems of construction and maintenance which occur in conventional engineering are encountered when producing software.The figure1.1illustrates how these three sections within a microcomputer are connected in terms of the communication of information within the machine. The system is controlled by the microprocessor which supervises the transfer of information betweenitself and the memory and input/output sections. The external connections relate to the rest (that is, the non-computer part) of the engineering system.Fig.1.1 Three Sections of a Typical MicrocomputerAlthough only one storage section has been shown in the diagram, in practice two distinct types of memory RAM and ROM are used. In each case, the word ‘memory’ is rather inappropriate since a computers memory is more like a filing cabinet in concept; information is stored in a set of numbered ‘boxes’ and it is referenced by the serial number of the ‘box’ in question.Microcomputers use RAM (Random Access Memory) into which data can be written and from which data can be read again when needed. This data can be read back from the memory in any sequence desired, and not necessarily the same order in which it was written, hence the expression ‘random’ access memory. Another type of ROM (Read Only Memory) is used to hold fixed patterns of information which cannot be affected by the microprocessor; these patterns are not lost when power is removed and are normally used to hold the program which defines the behavior of a microprocessor based system. ROMs can be read like RAMs, but unlike RAMs they cannot be used to store variable information. Some ROMs have their data patterns put in during manufacture, while others are programmable by the user by means of special equipment and are called programmable ROMs. The widely used programmable ROMs are erasable by means of special ultraviolet lamps and are referred to as EPROMs, short for Erasable Programmable Read Only Memories. Other new types of device can be erased electrically without the need for ultraviolet light, which are called Electrically Erasable Programmable Read Only Memories, EEPROMs.The microprocessor processes data under the control of the program, controlling the flow of information to and from memory and input/output devices. Some input/output devices are general-purpose types while others are designed for controlling specialhardware such as disc drives or controlling information transmission to other computers. Most types of I/O devices are programmable to some extent, allowing different modes of operation, while some actually contain special-purpose microprocessors to permit quite complex operations to be carried out without directly involving the main microprocessor.The microprocessor processes data under the control of the program, controlling the flow of information to and from memory and input/output devices. Some input/output devices are general-purpose types while others are designed for controlling special hardware such as disc drives or controlling information transmission to other computers. Most types of I/O devices are programmable to some extent, allowing different modes of operation, while some actually contain special-purpose microprocessors to permit quite complex operations to be carried out without directly involving the main microprocessor.The microprocessor , memory and input/output circuit may all be contained on the same integrated circuit provided that the application does not require too much program or data storage . This is usually the case in low-cost application such as the controllers used in microwave ovens and automatic washing machines . The use of single package allows considerable cost savings to e made when articles are manufactured in large quantities . As technology develops , more and more powerful processors and larger and larger amounts of memory are being incorporated into single chip microcomputers with resulting saving in assembly costs in the final products . For the foreseeable future , however , it will continue to be necessary to interconnect a number of integrated circuits to make a microcomputer whenever larger amounts of storage or input/output are required.Another major engineering application of microcomputers is in process control. Here the presence of the microcomputer is usually more apparent to the user because provision is normally made for programming the microcomputer for the particular application. In process control applications the benefits lf fitting the entire system on to single chip are usually outweighed by the high design cost involved, because this sort lf equipment is produced in smaller quantities. Moreover, process controllers are usually more complicated so that it is more difficult to make them as single integrated circuits. Two approaches are possible; the controller can be implemented as a general-purpose microcomputer rather like a more robust version lf a hobby computer, or as a ‘packaged’ system, signed for replacing controllers based on older technologies such as electromagnetic relays. In theformer case the system would probably be programmed in conventional programming languages such as the ones to9 be introduced later, while in the other case a special-purpose language might be used, for example one which allowed the function of the controller to be described in terms of relay interconnections, In either case programs can be stored in RAM, which allows them to be altered to suit changes in application, but this makes the overall system vulnerable to loss lf power unless batteries are used to ensure continuity of supply. Alternatively programs can be stored in ROM, in which case they virtually become part of the electronic ‘hardware’ and are often referred to as firmware. More sophisticated process controllers require minicomputers for their implementation, although the use lf large scale integrated circuits ‘the distinction between mini and microcomputers, Products and process controllers of various kinds represent the majority of present-day microcomputer applications, the exact figures depending on one’s interpretation of the word ‘product’. Virtually all engineering and scientific uses of microcomputers can be assigned to one or other of these categories. But in the system we most study Pressure and Pressure Transmitters. Pressure arises when a force is applied over an area. Provided the force is one Newton and uniformly over the area of one square meters, the pressure has been designated one Pascal. Pressure is a universal processing condition. It is also a condition of life on the planet: we live at the bottom of an atmospheric ocean that extends upward for many miles. This mass of air has weight, and this weight pressing downward causes atmospheric pressure. Water, a fundamental necessity of life, is supplied to most of us under pressure. In the typical process plant, pressure influences boiling point temperatures, condensing point temperatures, process efficiency, costs, and other important factors. The measurement and control of pressure or lack of it-vacuum-in the typical process plant is critical.The working instruments in the plant usually include simple pressure gauges, precision recorders and indicators, and pneumatic and electronic pressure transmitters. A pressure transmitter makes a pressure measurement and generates either a pneumatic or electrical signal output that is proportional to the pressure being sensed.In the process plant, it is impractical to locate the control instruments out in the place near the process. It is also true that most measurements are not easily transmitted from some remote location. Pressure measurement is an exception, but if a high pressure ofsome dangerous chemical is to be indicated or recorded several hundred feet from the point of measurement, a hazard may be from the pressure or from the chemical carried.To eliminate this problem, a signal transmission system was developed. This system is usually either pneumatic or electrical. And control instruments in one location. This makes it practical for a minimum number of operators to run the plant efficiently.When a pneumatic transmission system is employed, the measurement signal is converted into pneumatic signal by the transmitter scaled from 0 to 100 percent of the measurement value. This transmitter is mounted close to the point of measurement in the process. The transmitter output-air pressure for a pneumatic transmitter-is piped to the recording or control instrument. The standard output range for a pneumatic transmitter is 20 to 100kPa, which is almost universally used.When an electronic pressure transmitter is used, the pressure is converted to electrical signal that may be current or voltage. Its standard range is from 4 to 20mA DC for current signal or from 1 to 5V DC for voltage signal. Nowadays, another type of electrical signal, which is becoming common, is the digital or discrete signal. The use of instruments and control systems based on computer or forcing increased use of this type of signal.Sometimes it is important for analysis to obtain the parameters that describe the sensor/transmitter behavior. The gain is fairly simple to obtain once the span is known. Consider an electronic pressure transmitter with a range of 0～600kPa.The gain isdefined as the change in output divided by the change in input. In this case, the output is electrical signal (4～20mA DC) and the input is process pressure (0～600kPa). Thus the gain. Beside we must measure Temperature Temperature measurement is important in industrial control, as direct indications of system or product state and as indirect indications of such factors as reaction rates, energy flow, turbine efficiency, and lubricant quality. Present temperature scales have been in use for about 200 years, the earliest instruments were based on the thermal expansion of gases and liquids. Such filled systems are still employed, although many other types of instruments are available. Representative temperature sensors include: filled thermal systems, liquid-in-glass thermometers, thermocouples, resistance temperature detectors, thermostats, bimetallic devices, opticalkPamA kPa mA kPa kPa mA mA Kr 027.0600160600420==--=and radiation pyrometers and temperature-sensitive paints.Advantages of electrical systems include high accuracy and sensitivity, practicality of switching or scanning several measurements points, larger distances possible between measuring elements and controllers, replacement of components(rather than complete system), fast response, and ability to measure higher temperature. Among the electrical temperature sensors, thermocouples and resistance temperature detectors are most widely used.单片机系统广义地说，微处理系统是用于处理信息的，这种信息可以是电话交谈，仪器读数或企业帐户，但是各种情况下都涉及相同的主要操作：信息处理、存储和传递。
单片机外文文献
A: Fundamentals of Single-chip MicrocomputerT h e s i n g l e-c h i p m i c r o c o mp u t e r i s t h e c u l m i n a t i o n o f b o t h t h e d e v e l o p me n t o f t h e d i g i t a l c o mp u t e r a n d t h e i n t e g r a t e d c i r c u i t a r g u a b l y t h e t o w m o s t s i g n i f i c a n t i n v e n t i o n s o f t h e20t h c e n t u r yT h e s e t o w t y p e s o f a r c h i t e c t u r e a r e f o u n d i n s i n g l e-c h i p m i c r o c o m p u t e r.S o me e m p l o y t h e s p l i t p r o g r a m/d a t a m e mo r y o f t h e H a r v a r d a r c h i t e c t u r e,s h o w n i n F i g.3-5A-1,o t h e r s f o l l o w t h e p h i l o s o p h y, w i d e l y a d a p t e d f o r g e n e r a l-p u r p o s e c o mp u t e r s a n d m i c r o p r o c e s s o r s,o f m a k i n g n o l o g i c a l d i s t i n c t i o n b e t w e e n p r o g r a m a n d d a t a m e mo r y a s i n t h e P r i n c e t o n a r c h i t e c t u r e,s h o w n i n F i g.3-5A-2.I n g e n e r a l t e r m s a s i n g l e-c h i p m i c r o c o m p u t e r i s c h a r a c t e r i z e d b y t h e i n c o r p o r a t i o n o f a l l t h e u n i t s o f a c o m p u t e r i n t o a s i n g l e d e v i c e, a s s h o w n iFig.3-5A-1 A Harvard typeFig3-5A-3. Principal features of a microcomputerRead only memory (ROM)R O M i s u s u a l l y f o r t h e p e r m a n e n t, n o n-v o l a t i l e s t o r a g e o f a n a p p l i c a t i o n s p r o g r a m.M a n y m i c r o c o m p u t e r s a n d m i c r o c o n t r o l l e r s a r e i n t e n d e d f o r h i g h-v o l u m e a p p l i c a t i o n s a n d h e n c e t h e e c o n o m i c a l m a n u f a c t u r e o f t h e d e v i c e s r e q u i r e s t h a t t h e c o n t e n t s o f t h e p r o g r a m m e m o r y b e c o m m i t t e d p e r m a n e n t l y d u r i n g t h e m a n u f a c t u r e o f c h i p s.C l e a r l y,t h i s i m p l i e s a r i g o r o u s a p p r o a c h t o R O M c o d e d e v e l o p m e n t s i n c e c h a n g e s c a n n o t b e m a d e a f t e r m a n u f a c t u r e .T h i s d e v e l o p m e n t p r o c e s s m a y i n v o l v e e m u l a t i o n u s i n g a s o p h i s t i c a t e d d e v e l o p m e n t s y s t e m w i t h a h a r d w a r e e m u l a t i o n c a p a b i l i t y a s w e l l a s t h e u s e o f p o w e r f u l s o f t w a r e t o o l s.S o m e m a n u f a c t u r e r s p r o v i d e a d d i t i o n a l R O M o p t i o n s b y i n c l u d i n g i n t h e i r r a n g e d e v i c e s w i t h(o r i n t e n d e d f o r u s e w i t h)u s e r p r o g r a m m a b l e m e m o r y.T h e s i m p l e s t o f t h e s e i s u s u a l l y d e v i c e w h i c h c a n o p e r a t e i n a m i c r o p r o c e s s o r m o d e b y u s i n g s o m e o f t h e i n p u t/o u t p u t l i n e s a s a n a d d r e s s a n d d a t a b u s f o r a c c e s s i n g e x t e r n a l m e m o r y.T h i s t y p e o f d e v i c ec a n b e h a v e f u n c t i o n a l l y a s t h e s i n g l e c h i p m i c r o c o m p u t e r f r o m w h i c h i t i sd e r i v e d a l b e i t w i t h r e s t r i c t e d I/O a n d a mo d i f i e d e x t e r n a l c i r c u i t. T h e u s e o f t h e s e R O M l e s s d e v i c e s i s c o m m o n e v e n i n p r o d u c t i o n c i r c u i t s w h e r e t h e v o l u m e d o e s n o t j u s t i f y t h e d e v e l o p m e n t c o s t s o f c u s t o m o n-c h i p R O M[2];t h e r e c a n s t i l l b e a s i g n i f i c a n t s a v i n g i n I/O a n d o t h e r c h i p s c o mp a r e d t o a c o n v e n t i o n a l m i c r o p r o c e s s o r b a s e d c i r c u i t.M o r e e x a c t r e p l a c e m e n t f o r R O M d e v i c e s c a n b e o b t a i n e d i n t h e f o r m o f v a r i a n t s w i t h 'p i g g y-b a c k'E P R O M(E r a s a b l e p r o g r a m m a b l e R O M)s o c k e t s o r d e v i c e s w i t h E P R O M i n s t e a d o f R O M。
单片机英文文献
单片机英文文献Introduction of Programmable controllersFrom a simple heritage, these remarkable systems have evolved to not only replace electromechanical devices, but to solve an ever-increasing array of control problems in both process and nonprocess industries. By all indications, these microprocessor powered giants will continue to break new ground in the automated factory into the 1990s.HISTORYIn the 1960s, electromechanical devices were the order of the dayass far as control was concerned. These devices, commonly known as relays, were being used by the thousands to control many sequential-type manufacturing processes and stand-along machines. Many of these relays were in use in the transportation industry, more specifically, the automotive industry. These relays used hundreds of wires and their interconnections to effect a control solution. The performance of a relay was basically reliable - at least as a single device. But the common applications for relay panels called for 300 to 500 or more relays, and the reliability and maintenance issues associated with supporting these panels became a very great challenge. Cost became another issue, for in spite of the low cost of the relay itself, the installed cost of the panel could be quite high. The total costincluding purchased parts, wiring, and installation labor, could range from $30~$50 per relay. To make matters worse, the constantly changingneeds of a process called for recurring modifications of a control panel. With relays, this was a costly prospect, as it was accomplished by a major rewiring effort on the panel. In addition these changes were sometimes poorly documented, causing a second-shift maintenance nightmare months later. In light of this, it was not uncommon to discard an entire control panel in favor of a new one with the appropriate components wired in a manner suited for the new process. Add to this the unpredictable, and potentially high, cost of maintaining these systemsas on high-volume motor vehicle production lines, and it became clearthat something was needed to improve the control process – to make it more reliable, easier totroubleshoot, and more adaptable to changing control needs.That something, in the late 1960s, was the first programmable controller. This first ‘revolutionary’ systemwan developed as a specific response to the needs of the major automotive manufacturers in the United States. These early controllers, or programmable logic controllers (PLC), represented the first systems that 1 could be used on the factory floor, 2 could have there ‘logic’ changed without extensive rewiring orcomponent changes, and 3 were easy to diagnose and repair when problems occurred.It is interesting to observe the progress that has been made in the past 15 years in the programmable controller area. The pioneer products of the late 1960s must have been confusing and frightening to a greatnumber of people. For example, what happened to the hardwired and electromechanical devices that maintenance personnel were used to repairing with hand tools? They were replaced with ‘computers’ disguised as electronics designed to replace relays. Even the programming tools were designed to appear as relay equivalent presentations. We have the opportunity now to examine the promise, in retrospect, that the programmable controller brought to manufacturing.All programmable controllers consist of the basic functional blocks shown in Fig. 10. 1. We’ll examine each block to understand the relationship to the control system. First we look at the center, as itis the heart ( or at least the brain ) of the system. It consists of a microprocessor, logic memory for the storage of the actual control logic, storage or variable memory for use with data that will ordinarily change as a function power for the processor and memory. Next comes the I/O block. This function takes the control level signals for the CPU and converts them to voltage and current levels suitable for connection with factory grade sensors and actuators. The I/O type can range from digital (discrete or on / off), analog (continuously variable), or a variety of special purpose ‘smart’ I/O which are dedicated to a certain application task. The programmer is shown here, but it is normally used only to initially configure and program a system and is notrequired for the system to operate. It is also used in troubleshooting a system, and can prove to be a valuable tool in pinpointing the exact cause of a problem. The field devices shown here represent the varioussensors and actuators connected to the I/O. These are the arms, legs, eyes, and ears of the system, including push buttons, limit switches, proximity switches, photosensors, thermocouples, RTDS, position sensing devices, and bar code reader as input; and pilot lights, display devices, motor starters, DC and AC drives, solenoids, and printers as outputs.No single attempt could cover its rapidly changing scope, but three basic characteristics can be examined to give classify an industrial control device as a programmable controller. (1) Its basic internal operation is to solve logic from the beginning of memory to somespecified point, such as end of memory or end of program. Once the endis reached, the operation begins again at the beginning of memory. This scanning process continues from the time power is supplied to the timeit it removed.(2) The programming logic is a form of a relay ladder diagram. Normally open, normally closed contacts, and relay coils are used within a format utilizing a left and a right vertical rail. Power flow (symbolic positive electron flow) is used to determine which coil or outputs are energized or deenergized. (3) The machine is designed forthe industrial environment from its basic concept; this protection isnot added at a later date. The industrial environment includesunreliable AC power, high temperatures (0 to 60 degree Celsius), extremes of humidity, vibrations, RF noise, and other similar parameters. General application areasThe programmable controller is used in a wide variety of control applications today, many of which were not economically possible just a few years ago. This is true for two general reasons: 1 there cost effectiveness (that is, the cost per I/O point) has improveddramatically with the falling prices of microprocessors and related components, and 2 the ability of the controller to solve complex computation and communication tasks has made it possible to use it where a dedicated computer was previously used.Applications for programmable controllers can be categorized in a number of different ways, including general and industrial application categories. But it is important to understand the framework in which controllers are presently understood and used so that the full scope of present and future evolution can be examined. It is through the power of applications that controllers can be seen in their full light.Industrial applications include many in both discrete manufacturing and process industries. Automotive industry applications, the genesis of the programmable controller, continue to provide the largest base of opportunity. Other industries, such as food processing and utilities, provide current development opportunities.There are five general application areas in which programmable controllers are used. A typical installation will use one or more of these integrated to the control system problem. The five general areas are explained briefly below.DescriptionThe AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of Flash programmable and erasable read only memory (PEROM). The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible withthe industry-standard MCS-51 instruction set and pinout. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C51is a powerful microcomputer which provides a highly-flexible and cost-effective solution to many embedded control applications.Function characteristicThe AT89C51 provides the following standard features: 4K bytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters, a five vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator and clock circuitry. In addition, the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port andinterrupt system to continue functioning. The Power-down Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset.Pin Description:VCCSupply voltage.:GNDGround.:Port 0Port 0 is an 8-bit open-drain bi-directional I/O port. As an output port, each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as highimpedance inputs.Port 0 may also be configured to be the multiplexed loworder address/data bus during accesses to external program and data memory. In this mode P0 has internal pullups.Port 0 also receives the code bytes during Flash programming,and outputs the code bytes during programverification. External pullups are required during programverification.Port 1Port 1 is an 8-bit bi-directional I/O port with internal pullups.The Port 1 output buffers can sink/source four TTL inputs.When 1s are written to Port 1 pins they are pulled high by the internal pullups and can be used as inputs. As inputs,Port 1 pins that are externally being pulled low will source current (IIL) because of the internalpullups.Port 1 also receives the low-order address bytes during Flash programming and verification.Port 2Port 2 is an 8-bit bi-directional I/O port with internal pullups.The Port 2 output buffers can sink/source four TTL inputs.When 1s are written to Port 2 pins they are pulled high by the internal pullups and can be used as inputs. As inputs,Port 2 pins that are externally being pulled low will source current, because of the internal pullups.Port 2 emits the high-order address byte during fetches from external programmemory and during accesses to external data memory that use 16-bit addresses. In this application, it uses strong internal pullupswhen emitting 1s. During accesses to external data memory that use 8-bit addresses, Port 2 emits the contents of the P2 Special Function Register.Port 2 also receives the high-order address bits and some control signals during Flash programming and verification.Port 3Port 3 is an 8-bit bi-directional I/O port with internal pullups.The Port 3 output buffers can sink/source four TTL inputs.When 1s arewritten to Port 3 pins they are pulled high by the internal pullups and can be used as inputs. As inputs,Port 3 pins that are externally being pulled low will source current (IIL) because of the pullups.Port 3 also serves the functions of various special features of the AT89C51 aslisted below:Port 3 also receives some control signals for Flash programming and verification.RSTReset input. A high on this pin for two machine cycles while the oscillator is running resets the device. ALE/PROGAddress Latch Enable output pulse for latching the low byte of the address during accesses to external memory. This pin is also the program pulse input (PROG) during Flash programming.In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency, and may beused for external timing or clocking purposes. Note, however, that one ALE pulse is skipped during each access to external Data Memory.If desired, ALE operation can be disabled by setting bit 0 of SFR location 8EH. With the bit set, ALE is active only during a MOVX or MOVC instruction. Otherwise, the pin is weakly pulled high. Setting the ALE-disable bit has no effect if the microcontroller is in external execution mode.PSENProgram Store Enable is the read strobe to external program memory.When the AT89C51 is executing code from external program memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory.EA/VPPExternal Access Enable. EA must be strapped to GND in order toenable the device to fetch code from external program memory locations starting at 0000H up to FFFFH. Note, however, that if lock bit 1 is programmed, EA will be internally latched on reset.EA should be strapped to VCC for internal program executions.This pin also receives the 12-volt programming enable voltage(VPP) during Flash programming, for parts that require12-volt VPP.XTAL1Input to the inverting oscillator amplifier and input to theinternal clock operating circuit. XTAL2Output from the inverting oscillator amplifier.Oscillator CharacteristicsXTAL1 and XTAL2 are the input and output, respectively,of aninverting amplifier which can be configured for use as an on-chip oscillator, as shown in Figure 1.Either a quartz crystal or ceramic resonator may be used. To drive the device from an external clock source, XTAL2 should be left unconnected while XTAL1 is driven as shown inFigure 2.There are no requirements on the duty cycle of the external clock signal, since the input to the internal clocking circuitry is through a divide-by-two flip-flop, but minimum and maximum voltage high and low time specifications must be observed.Figure 1. Oscillator Connections Figure 2. External Clock Drive ConfigurationIdle ModeIn idle mode, the CPU puts itself to sleep while all the onchip peripherals remain active. The mode is invoked by software. The content of the on-chip RAM and all the special functions registers remain unchanged during this mode. The idle mode can be terminated by any enabled interrupt or by a hardwarereset.It should be noted that when idle is terminated by a hard ware reset, the device normally resumes program execution,from where it left off, up to two machine cycles before the internal reset algorithm takes control. On-chip hardware inhibits access to internal RAM in this event, but access to the port pins is not inhibited. To eliminate thepossibility of an unexpected write to a port pin when Idle is terminatedby reset, the instruction following the one that invokes Idle should not be one that writes to a port pin or to external memory.Power-down ModeIn the power-down mode, the oscillator is stopped, and theinstruction that invokes power-down is the last instruction executed. The on-chip RAM and Special Function Registers retain their values until the power-down mode is terminated. The only exit from power-down is a hardware reset. Reset redefines the SFRs but does not change the on-chip RAM. The reset should not be activated before VCC is restored to its normal operating level and must be held active long enough to allow the oscillator to restart and stabilize.Program Memory Lock BitsOn the chip are three lock bits which can be left unprogrammed (U)or can be programmed (P) to obtain the additional features listed in the table below.When lock bit 1 is programmed, the logic level at the EA pin is sampled and latched during reset. If the device is powered up without a reset, the latch initializes to a random value, and holds that value until reset is activated. It is necessary that the latched value of EA be in agreement with the current logic level介绍可编程控制器从简单的遗产，这些不寻常的系统已经发展到不仅取代机电设备，而是解决问题的控制日益增加的过程和非过程中一系列行业的腾飞。
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单片机英文文献Principle of MCUSingle-chip is an integrated on a single chip a complete computer system. Even though most of his features in a small chip, but it has a need to complete the majority of computer components: CPU, memory, internal and external bus system, most will have the Core. At the same time, such as integrated communication interfaces, timers, real-time clock and other peripheral equipment. And now the most powerful single-chip microcomputer system can even voice, image, networking, input and output complex system integration on a single chip.Also known as single-chip MCU (Microcontroller), because it was first used in the field of industrial control. Only by the single-chip CPU chip developed from the dedicated processor. The design concept is the first by a large number of peripherals and CPU in a single chip, the computer system so that smaller, more easily integrated into the complex and demanding on the volume control devices. INTEL the Z80 is one of the first design in accordance with the idea of the processor, From then on, the MCU and the development of a dedicated processor parted ways.Early single-chip 8-bit or all of the four. One of the most successful is INTEL's 8031, because the performance of a simple and reliable access to a lot of good praise. Since then in 8031 to develop a single-chip microcomputer system MCS51 series. Based on single-chip microcomputer system of the system is still widely used until now. As the field of industrial control requirements increase in the beginning of a 16-bit single-chip, but not ideal because the price has not been very widely used. After the 90's with the big consumer electronics product development, single-chip technology is a huge improvement. INTEL i960 Series with subsequent ARM in particular, a broad range of applications, quickly replaced by 32-bit single-chip 16-bit single-chip high-end status, and enter the mainstream market. Traditional 8-bit single-chip performance has been the rapid increase in processing power compared to the 80's to raise a few hundred times. At present, the high-end 32-bit single-chip frequency over 300MHz, the performance of the mid-90's close on the heels of a special processor, while the ordinary price of the model dropped to one U.S. dollars, the most high-end models, only 10 U.S. dollars. Contemporary single-chip microcomputer system is no longer only the bare-metal environment in the development and use of a large number of dedicated embedded operating system is widely used in the full range of single-chip microcomputer. In PDAs and cell phones as the core processing of high-end single-chip or even a dedicated direct access to Windows and Linux operating systems.More than a dedicated single-chip processor suitable for embedded systems, so it was up to the application. In fact the number of single-chip is the world's largest computer. Modern human life used in almost every piece of electronic and mechanical products will have a single-chip integration. Phone, telephone, calculator, home appliances, electronic toys, handheld computers and computer accessories such as a mouse in the Department are equipped with 1-2 single chip. And personal computers also have a large number of single-chip microcomputer in the workplace. Vehicles equipped with more than 40 Department of the general single-chip, complex industrial control systems and even single-chip may have hundreds of work at the same time! SCM is not only far exceeds the number of PC and other integrated computing, even more than the number of human beings.Hardwave introductionThe 8051 family of micro controllers is based on an architecture which is highly optimized for embedded control systems. It is used in a wide variety of applications from military equipment to automobiles to the keyboard on your PC. Second only to the Motorola 68HC11 in eight bit processors sales, the 8051 family of microcontrollers is available in a wide array of variations from manufacturers such as Intel, Philips, and Siemens. These manufacturers have added numerous features and peripherals to the 8051 such as I2C interfaces, analog to digital converters, watchdog timers, and pulse width modulated outputs. Variations of the 8051 with clock speeds up to 40MHz and voltage requirements down to 1.5 volts are available. This wide range of parts based on one core makes the 8051 family an excellent choice as the base architecture for a company's entire line of products since it can perform many functions and developers will only have to learn this one platform.The basic architecture consists of the following features:·an eight bit ALU·32 descrete I/O pins (4 groups of 8) which can be individually accessed·two 16 bit timer/counters·full duplex UART· 6 interrupt sources with 2 priority levels·128 bytes of on board RAM·separate 64K byte address spaces for DA TA and CODE memoryOne 8051 processor cycle consists of twelve oscillator periods. Each of the twelve oscillator periods is used for a special function by the 8051 core such as op code fetches and samples of the interrupt daisy chain for pending interrupts. The time required for any 8051 instruction can be computed by dividing the clock frequency by 12, inverting that result and multiplying it by the number of processor cycles required by the instruction in question. Therefore, if you have a system which is using an 11.059MHz clock, you can compute the number of instructions per second by dividing this value by 12. This gives an instruction frequency of 921583 instructions per second. Inverting this will provide the amount of time taken by each instruction cycle (1.085 microseconds).单片机原理单片机是指一个集成在一块芯片上的完整计算机系统。