| With the increasing complexity of the weapon system, the Testability and Fault Detection is an important means by which the perfection of weapon equipment and the reduce of using cost or maintenance cost, are accessible. Automatic Testing and Fault Isolation can make the MTTR of system be reduced, or enhance the availability of system. At the meantime, it can decrease the mount of maintenance men or reduce the technical standard of them. Thus, it'll attain the object that the using cost and maintenance cost reduce. But it can also increase the weigh ,size ,complexity and cost at the same time , so the weight is necessary at the beginning of the system design.In this paper, a new method for testability of Dimming and Focusing Autonomous System in Electro-optic Theodolite is introduced, that is BIT (Build-in Test). Testability is a new subject which came into being in 1970's, but the research of this subject in our country is late, and the research about testability in this field is not begin. The definition of BIT is that the system or equipment has a ability of automatic test and fault isolation, BIT is a important technology for improvement of testability, it can be used in watching for running condition of system continuously or periodically, or watch and diagnostic before maintain .in this text, the objective value of fault detection ratio reach to the degree of 95 percent and the lowest of it reach to the degree of 85 percent through the method of BIT.Testing system, in which DSP is the part of core and CPLD is as peripheral circuit, controls operation parts, and test or incept the digital signal,analog signals and switch signals from exterior.In the paper DSP of TMS320 family is used as key parts of an apparatus, TMS320 family consists of three following generations: C2000, C5000, C6000. It is the 16-bit fixed-point DSP of low price and high capability which is produced by TI company in 1997.It has Separate program and data spaces, this allow simultaneous access to program memorizer and data memorizer, because the 'C24x DSP architecture is based on a modified Harvard architecture, which supports separate bus structures for program space and data space. So this can increase the running speed of system greatly.DSP's interface resources are applied fully: pulse width modulate is applied to as operation signal of direct current motor, at the same time ,a port is used for control of forth and back running of motor. Because DSP has analog-digital conversion interface of 10 bit, this type of interface act as sampling of analog quantity. A piece of memorizer 6416 act as extend of external memorize in which the program and data space are 32K respectively. Exterior LCD,switch signals and serial extend port are got independently address distribution . CC2000 soft ware is adopted , which is producted by Texas Instrument Incorporation for TMS320C2XX. DSP program is exploited base on C language speeds up the velocity of DSP exploitage, furthermore ,it's readability and transplantable ability enhance greatly. Modification of program is also convenient. But on some conditions, the efficiency of C code is lower than it of assembly language by hand, Even though the best C compiler, can not always utilize DSP resource in the best condition. DSP's control of hardware which is gotten by using C language is less convenient than assembly program. sometimes ,control can not acquire by C language. So in this testing system, C language and assembly language are alternate using, this can access to utilize all of DSP's resource in the best extend.As to Periphery CPLD, EPM7256S in MAX7000 series which can provide the most quickly velocity is adopt, it base on COMS EEPROM technics and transmit delay is 3.5ns on least value, it's act velocity is quicker than 200Mhz counter. Moreover it is compatible with PIC, so it is adapt to high speed design. The manner of connection can change act on the manner of programme to CPLD, this can make debugging more convenient and make use of the resource on the circuit board.
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