CC BY
28
Section 2. Information technology
DOI: http://dx.doi.org/10.20534/AJT-17-3.4-7-10
Djuraev Rustam Хusanovich) Senior Lecturer
Tashkent University of Information Technologies Dpt. of Data communication networks and systems
Tashkent
Djabbarov Shuxrat Yuldashevich, Ph. D. assistant professor
Tashkent University of Information Technologies Dpt. of Data communication networks and systems
Tashkent
Baltaev Jo'shqin Boltabaevich, Assistant
Tashkent University of Information Technologies Dpt. of Data communication networks and systems
Tashkent E-mail: jowkin@mail.ru
Diagnosis of multiple-output microprocessor devices and methods of reference signature calculation
Abstract: Issues of diagnosis and approaches of using of signature analysis for diagnosis of multiple-output digital devices are considered in this paper. Methods of signatures calculation for signature analysis are given. Algorithm and software for automation of reference digital signature calculation is given.
Keywords: Microprocessor sets, data communication equipment, large scale integration, very large scale integration, technical replacement element, signature analyzer, multichannel signature analyzer.
The transition to the widespread use of (MPS) in the Of the many areas of diagnostics features the latest
modern data communication equipment (DCE) has cre- combination of test and functional diagnosis, in which
ated a number of serious problems associated with the the means of functional diagnostics assign a task only
processes of diagnosis. prompt discovery of the fault, and the search for the
Modern DCE has a wide range of digital cards which failed component is carried out by the means of test di-use various element bases. The widespread use of LSI agnosis. In terms of the DCE exploitation, troubleshoot-(large scale integration), VLSI () and MPS in the DCE ing control sequence is as follows: DCE, unit (subunit), a have established together with the indisputable advan- technical replacement element (TRE), the individual intages a number of serious problems in their operational tegrated circuits and electric radio elements. services primarily related to the processes of monitoring One of the microprocessor systems strong external and fault diagnosis [1-3]. diagnosis tools is a signature analyzer (SA) [1-3]. The
Improving the technical and operational characteris- principle of operation is based on the signature analysis,
tics of the complex DCE-based LSI, VLSI and MPS is in- i. e. compression of long sequences of a 4-digit 16 hexa-
extricably linked with the development of techniques decimal signatures. Physically, this method is imple-
and methods of diagnosis with the need to analyze mul- mented in a linear shift register with feedback signals
tiple-output digital device signatures. which are summed by modulo 2 with the input sequence.
The problem of multiple-output analysis of digital devices and the process of testing is to identify a fault circuit on its output reactions. The distinguishing feature of this type of analysis is the need to study a sufficiently large number of output responses, therefore, the use of traditional methods of compact testing which are used for single-output digital circuits, in this case, does not allow us to obtain the desired effect. Analysis of n - digital output circuit monophonic signature analyzer (SA) increases the time required for circuit analysis by n times or the hardware required to implement the n signature analyzers. Therefore, in practice multichannel signature analyzer often is used. (MSA) The signature of the multichannel signature analyzer S (y) is uniquely determined by the number of n investigated schemes outputs. Therefore, as n increases the complexity of the compression device and the number of bits used to represent the signature S(y), takes almost an invalid size.
An important parameter of the signature analysis is the set of reference signatures, which is determined in advance for correct digital device. The need to establish methods for the calculation of signatures associated with the need to automate the production of dictionaries (tables) reference signatures, since their creation by measuring the signature is quite time consuming. Therefore, the basic document of signature analysis is the standard signature dictionary, which defines the troubleshooting algorithm.
At present, there are various theoretical methods for calculating the reference signatures [2-5].
Calculation method of the reference signatures based on the analysis of the SA
As you know, the essence of the SA is that the data sequences from the node of the properly functioning circuit in the test mode are set in accordance with a specific signature. During the next test of this scheme, operator with a signature analyzer measures at different points in the digital circuit unit and compares them with before taken reference signatures in the documents. The principle of operation is based on the SA method of signature analysis, ie compression of long sequences in the four-digit hexadecimal signature. Physically, this method is implemented in a linear shift register with feedback signals, which are summed by modulo two with the input sequence. As polynomial irreducible polynomial is used: P(X) = x 16 + x12 + x 9 + x 7 +1
Signatures are reproduced, usually in the alphabet consisting of six to ten digits and letters: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, C, F, H, P, U. Each binary sequence has its own signature.
0000 — "0" 0100 — "4" 1000 — "8" 1100 — "F"
0001 — "1" 0101 — "5" 1001 — "9" 1101 — "H"
0010 — "2" 0110 — "6" 1010 — "A" 1110 — "P"
0011 — "3" 0111 — "7" 1011 — "C" 1111 — "U"
The signature is generated using a shift register with
feedback logic P(x) = x16+x 12+ x9+x7+1, at which input is modulo two adder. Assume that during the connection of the probe parser to any reference point, it occurred 20 - bit sequence of ones and zeros having the form: 11111100000111111111. This input sequence is added by modulo 2 to the contents of the cells 7, 9, 12 and 16 of the shift register. After 20 cycles of the scheme in the register will be 16-bit combination is 1101100101010011, which as a result of the division into four four-digit alphanumeric combinations corresponds to - the digital signature of H953.
A simplified method for calculating the reference signatures
As noted previously, the method of the SA is to compress the output responses of the subjects of electronic components with the help of the shift register with logic feedback in short words — the signature. Implementation principle of the SA generally is based on the mathematical ratios, similar to those used in the formation of the cyclic codes. However, due to the fact that the practical scheme of the divider is made on multi-input adders modulo-2 differs from that used divider cyclic code, the contents of the shift register and the result of division of SA, F(x) on P(X) is not the same. It is known that the residue obtained in the shift register is of the form R(x) = = x15 + x14 + x12 + x11 + x8 + x6 + x4 + x + 1, and the remainder after dividing the F(X) at F'(x) has the form: x15 + x14 + x12 + x11 + x7.
In this regard, it is necessary to analyze not the remainder of the division, but the quotient. In accordance with this method, a signature is calculated by multiplying the input polynomial F(X) by a monomial XR and dividing this product by the inverse generator polynomial
F (X X = Q(X ) + *(X)
(1)
P '(X ) P '(X )
In this case, the quotient has the same degree as F
(X), and the signature is the last r bits.
rXX) = [Q(X)] mod 2r
Consider the example of a theoretical calculation of
the signature for this method for similar to the previously
considered the input sequence. Multiplying the input
polynomial F (X) by a monomial X16 obtain:
f(x) X 16 = x35 + x 34+ x 33 + x32 + x 31 + x30 + x 29+ x 23 +
+x 22+ x 21 + x 20 + x 19 + +x 18 +X 17 + x 16.
We divide this polynomial by a polynomial inverse P'(X)=x16+x 9+x 7+x4+1.
As a result, we obtain quotient, Q(X) = x 19 + x 18+ x 17 + x16 + x 15 + x 14 + x13+ +x12+ x 11 + x8 + x 6+ x4 +x+1. And the remainder, R(X) = x 15 + x 13+ x10 + x 9 + x8 + x 7 + x 6+ +x 2+ x
Transforming Q(X) into the binary form we obtain Q(X) = 11111100100101010011
The last 16 bits of the method are the signature, i. e.
1101100101010011 corresponds to the signature of H953.
Method for determination of signatures based on modeling the signature analyzer
The simulation program of the signature method diagnosis for digital devices SIGNATURA is designed to indicate the process of forming a digital signature for the diagnosis of the device [5]. The program simulates the process of passing through a sequence ofdigital logic circuit consisting ofa shift register and modulo-2 adder. After the simulation, the program produces results - a digital signature in the form of a code is displayed on the seven-segment display.
The program requires no installation, and is started by running the application signatura.exe. When you run the program, a window appears.
The program window contains the image of the simulated circuit at the top, and at the bottom — the controls.
The sequence of operation of the program is as follows:
- Set the bit shift register;
- Set the level of the polynomial;
- Introduce an input sequence;
- If necessary, set the interval for acceleration/deceleration process;
- Press the "Start" button.
When you click on "Start" to the input of the adder modulo 2 an input sequence starts being supplied. The levels of the input sequence pass through logic circuit and are stored in the shift register.
When all the bits of the input sequence pass through the logic circuit appears on the screen a digital signature, which is a code for the seven-segment display (Figure 1).
Figure 1. The digital signature after the process finished
Each character of the signature is displayed under the corresponding four bits of the shift register. To the hexadecimal register corresponds a four-character signature, to the eight-bit - a two-character, for the thirty-bit - an eight character signature corresponds.
Thus, the following results were obtained: Proposed the simplified method ofcalculating the reference signatures, which has lower complexity, and free from shortcomings that are inherent in the known theoretical methods for calculating the reference signatures.
In order to automate the definition of the reference signatures a new algorithm and simulation program of the signature method diagnosis for digital devices are developed.
The developed software is compatible with operating systems Microsoft Windows NT/2000/XP/2003/7.
Conclusion
1. Analysis of the characteristics of existing control and diagnostic tools showed that practically only methods and means of signature analysis is ready to use in the maintenance.
2. Proposed the simplified method of calculating the reference signatures, which has lower complexity, and free from shortcomings that are inherent in the known theoretical methods for calculating the reference signatures.
3. In order to automate the definition of the reference signatures a new algorithm and simulation program of the signature method diagnosis for digital devices are developed.
References:
1. Бестугин А.Р, Богданова А.Ф, Стогов Г. В. Контроль и диагностирование телекоммуникационных сетей -СПб: Политехника, - 2003. - 174 с.: ил.
2. Арипов М. Н. Джураев Р. Х., Джаббаров Ш. Ю. Техническая диагностика цифровых систем. Учебное пособие - Ташкент - 2006.
3. Хаханов В. И. Техническая диагностика цифровых и микропроцессорных структур. Учебник. - К.: I3MH, -1995. - 252 с.
4. Джаббаров Ш. Ю. «Принципы диагностики цифровых устройств средствами сигнатурного анализа». Тош ДТУ Хабарлари. - 2006, - № 2. - С. 29-31.
5. Джураев Р. Х., Джаббаров Ш. Ю., Янгалиев Ф. Ш., Программа моделирования сигнатурного метода диагностики цифровых устройств.// - № DGU 01244, - 26.03.2007.
