【導(dǎo)讀】單片機廣泛應(yīng)用于商業(yè)：諸如調(diào)制解調(diào)器，電動機控制系統(tǒng)，空調(diào)控制系統(tǒng)，這些單片機的高速處理速度和增強型外圍設(shè)備集合。然而，這些關(guān)鍵應(yīng)用領(lǐng)域也要求這些單。健壯的測試環(huán)境和用于驗證這些無論在元部件層次還是系統(tǒng)級別。的單片機的合適的工具環(huán)境保證了高可靠性和低市場風(fēng)險。開發(fā)了一種面向?qū)ο蟮挠糜隍炞C它的AT89C51汽車單片機多線性測試環(huán)境。能夠容易擴展并重復(fù)用來驗證其他幾種將來的單片機。MCS51單片機典型的應(yīng)用是高速事件控制系統(tǒng)。車工業(yè)把MCS51單片機用于發(fā)動機控制系統(tǒng)，懸掛系統(tǒng)和反鎖制動系統(tǒng)。擁有操作不可預(yù)測的設(shè)備的經(jīng)濟和法律風(fēng)險是很高的。圍設(shè)計缺陷的話，費用會更高。IntelChandler平臺工程組提供了各種單片機和處。同時，AT89C51降至0Hz的靜態(tài)邏輯操作，并支持兩種可選的節(jié)電。掉電方式保存RAM中的內(nèi)容，但振蕩器體制工作并禁止其他。行外部程序時，應(yīng)設(shè)置ALE無效。在此期間，當(dāng)訪問外部數(shù)據(jù)存儲器，這兩次有效的PSEN信號不出現(xiàn)。·XTAL1：振蕩器反相放大器及內(nèi)部時鐘發(fā)生器的輸入端。

　　

【正文】 Program Verify: If lock bits LB1 and LB2 have not been programmed, the programmed code data can be read back via the address and data lines for verification. The lock bits cannot be verified directly. Verification of the lock bits is achieved by observing that their features are enabled. Chip Erase: The entire Flash array is erased electrically by using the proper bination of control signals and by holding ALE/PROG low for 10 ms. The code array is written with all “1”s. The chip erase operation must be executed before the code memory can be reprogrammed. Reading the Signature Bytes: The signature bytes are read by the same procedure as a normal verification of locations 030H, 031H, and 032H, except that and must be pulled to a logic low. The values returned areas follows : (030H) = 1EH indicates manufactured by Atmel (031H) = 51H indicates 89C51 (032H) = FFH indicates 12V programming (032H) = 05H indicates 5V programming Programming Interface Every code byte in the Flash array can be written and the entire array can be erased by using the appropriate bination of control signals. The write operation cycle is self timed and once initiated, will automatically time itself to pletion. A microputer interface converts information between two forms. Outside the microputer the information handled by an electronic system exists as a physical signal, but within the program, it is represented numerically. The function of any interface can be broken down into a number of operations which modify the data in some way, so that the process of conversion between the external and internal forms is carried out in a number of steps. An analogtodigital converter is used to convert a continuously variable signal to a corresponding digital form which can take any one of a fixed number of possible binary values. If the output of the transducer does not vary continuously, no ADC is necessary. In this case the signal conditioning section must convert the ining signal to a form which can be connected directly to the next part of the interface, the input/output section of the microputer itself. Output interfaces take a similar form, the obvious difference being that here the flow of information is in the opposite direction。 it is passed from the program to the outside world. In this case the program may call an output subroutine which supervises the operation of the interface and performs the scaling numbers which may be needed for digitaltoanalog converter. This subroutine passes information in turn to an output device which produces a corresponding electrical signal, which could be converted into analog form using a DAC. Finally the signal is conditioned to a form suitable for operating an actuator. The signals used within microputer circuits are almost always too small to be connected directly to the outside world” and some kind of interface must be used to translate them to a more appropriate form. The design of section of interface circuits is one of the most important tasks facing the engineer wishing to apply microputers. We have seen that in microputers information is represented as discrete patterns of bits。 this digital form is most useful when the microputer is to be connected to equipment which can only be switched on or off, where each bit might represent the state of a switch or actuator. To solve realworld problems, a microcontroller must have more than just a CPU, a program, and a data memory. In addition, it must contain hardware allowing the CPU to access information from the outside world. Once the CPU gathers information and processes the data, it must also be able to effect change on some portion of the outside world. These hardware devices, called peripherals, are the CPU’s window to the outside. The most basic form of peripheral available on microcontrollers is the general purpose I70 port. Each of the I/O pins can be used as either an input or an output. The function of each pin is determined by setting or clearing corresponding bits in a corresponding data direction register during the initialization stage of a program. Each output pin may be driven to either a logic one or a logic zero by using CPU instructions to pin may be viewed (or read.) by the CPU using program instructions. Some type of serial unit is included on microcontrollers to allow the CPU to municate bitserially with external devices. Using a bit serial format instead of bitparallel format requires fewer I/O pins to perform the munication function, which makes it less expensive, but slower. Serial transmissions are performed either synchronously or asynchronously.