SU1735850A1 - Transistor-transistor logic unit 1/o state diagnosis method - Google Patents

Abstract

The invention relates to automation and computing and coins to find application for monitoring and diagnosing transistor-transistor logic (TTL) elements and devices. The aim of the invention is to increase the reliability of diagnostics in the detection and localization of interconnect defects, as well as input and output cascades of TTL devices. For this purpose, the diagnostics is carried out in two stages. At the first stage, the operability of the inputs of the device under diagnosis is determined by its OTA switch on the load and measuring the static value in the common bus for each test set and determining the difference between the measured and calculated current values in the common bus, and The second stage determines the health of the outputs of the diagnostics object after they are connected to the load and compares the measured and calculated values of the consumption currents in the power bus and the common bus. 2 ill., 8 tab. (L with

Description

The invention relates to automation and computing and can be used to monitor and diagnose transistor-transistor logic (TTL) elements and devices.

The object of the invention is to increase the reliability of diagnosis in the detection and localization of interconnect defects, as well as input and output cascades of TTL devices.

Fig. 1 shows a functional diagram for connecting a diagnosed logic device to a power source; Fig. 2 is a circuit diagram of a basic logic element (BS) "

Figure 1 shows the diagnosed logical device 1, source 2

power supply, connected by power bus 3 and common bus 4. Device 1 also has inputs 5 and outputs 6.

The basic logic element of the device .1 (FIG. 2) contains a multi-emitter transistor T1 7, transistors 8-10 (T2, T3 and T4), a diode 11 and resistors 12-15 (R1, R2, R3 and R4).

The method is as follows. in a way.

In the nerve stage, the definition is wrong. the availability of the input connecting lines of a TTL device, i.e. the absence of interruptions or short circuits, as well as the correctness of the input stages of the logical device itself; For this, the outputs of the diagnosed device are disconnected from the load and under various test actions measuring -4

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consumption currents flowing in the power rail and the common bus are bored. For each test set, the difference between the value of the static current flowing in the diagnostics power supply bus and the value of the static current flowing in the common bus is determined.

The resulting difference in the current consumption of a logical device (LU) flowing in the power bus and the common bus is the total input current of the LU, the value of which depends on the health or possible malfunction of the inputs of the TTL device, as well as on the test set present at the inputs.

The calculated difference is compared with the reference value of the input current of the diagnosed LU, which is determined by the formula

N g m ..

AW -a, -D), ()

where UIfloT. - the difference between the currents flowing in the power bus and the common bus when the diagnostics object outputs are disconnected and the j-th input action

N is the number of basic logic elements (BLE) of TTL devices, whose inputs are the inputs of the diagnostic object J

a | - proportionality factor, numerically equal to the value of the input current of one BLA with zero input effect;

Xp, is the value of the logical signal at the -th input and the 1st BLA, and the logical signals can take values from the basis of Јo, 1-j J m is the number of BLA whose inputs are the inputs of the diagnosed LU.

According to the mismatch between the actual value of the input current and the reference value corresponding to the good condition, the LN inputs determine the type of fault and its place.

At the second stage of diagnostics, the health of the outputs of the diagnostic object is determined, for which the outputs of the TTL device are connected to the load, test effects are fed to the device inputs, the static consumption currents in the power bus and the common bus of the diagnostic object are measured, the latter is compared with reference value, which is determined by the formula

five

U

- Z:

SWEAT. J

X,

 Ui

sweat yea I

+ Ka,

P

(12)

five

0

five

0

five

0

five

where u i

sweat.

J

the difference between the values of the currents flowing in the power bus and the common diagnostics bus at the jth input action, Z is the value of the logic signal at the ith output of the logic device at the jth input action in the basis of fo, ll1, n is the number of outputs of the object being diagnosed, & 2 proportionality coefficient, numerically equal to the output current at zero output,

K - the number of BLA, the inputs of which are connected to the i-th output of the diagnosed object.

In this case, in the expression (2), the actual value of DI Pot B, measured at the first stage of diagnosis, is substituted.

The absence of a mismatch between the actual and reference values of the current difference indicates the good condition of the outputs of the diagnosed device. If there is a mismatch, the magnitude of the latter, as well as the value of the logical variables, indicate the nature and location of the malfunction. The simplest and most compelling example of a controlled logical device is a multiplexer made in the form of an integrated circuit (IC).

Specifically, was selected K155 KP2 (dual multiplexer). For impartiality, it is necessary to show not only the difference of the currents, but also the magnitudes of the currents themselves, flowing in the bus power and the total power of the object of diagnosis.

With the break of the connecting line 25 STU5 ° SCHA to such a test set, at the j-ro input, as well as a short circuit - which is not present at the j-th input

the signal of logical zero, has the form given in table. 2

No j-ro entry of the IC K 155 KP2 to the power bus line 1–9 of the table. 1, corresponding to

In the event of a short circuit on the common bus of the 1st input (resolution input) of the IC K 155 KP2, the table of the reactions of the IC to test actions will become as shown in Table. 3

Table 3

Continuation of the table „.3

40

45

In the event of a short circuit on the common bus of the 2nd input (input of the choice) of the IC K 155 S12 table. 1 will take the following form (Table 4).

7 1

Table 4

In case of a short circuit of the 3rd input (data input) of the IC K 155 KPZ, the response of the object of diagnosis to test influences has the values given in Table. five.

Table 5

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 At the second stage of diagnosing the response of the object to be diagnosed with one output connected (the seventh pin of the IC K 155 1SH2) have the meanings given in Table. 6

Table 6

five

The results are shown in Table. 6 are treated as follows.

During the first / test action, the input current is absent; therefore, the difference in the currents L1 reflects only the output current. With the second test action, there is no output current, and D1 is equal to the input current. In the third test action, the input and output currents cancel each other out (the output current is flowing, so in the analytical expression, when calculating the reference value, it is taken with a negative sign).

The connection of two logic inputs to the output of the IC K 155 1Ш2 determines the reactions listed in Table. 7

Table,

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91735850

tabl. 7

t ave us t t shi

Reactions

Test

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II

37.1

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n

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n m

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II

30.4

31.5

Connecting eight logic inputs at the first test exposure gives the results given in Table. eight,

Table 8

35.4

44.2

-8,8

An output breakage will lead to a retreat of the output current and the response of the object will correspond to the reactions given in Table. one.

Short-circuiting the output to the power bus or the common bus will lead to a multiple increase in the output current and, therefore, to a distortion of the reactions given in Table. 6

Claims (1)

Invention Formula A method for diagnosing the state of the inputs-outputs of transistor-transistor logic devices, which includes feeding test inputs to the device inputs and measuring the static current consumed by the logic device in the power bus, which is determined, in order to increase the reliability, five Testing is carried out in two stages, with the atom at the first stage determining the operability of the inputs of the device being diagnosed, for which the outputs of the latter are disconnected from the load, for each test set the static value of the current flowing in the common bus is measured, the difference between ... By comparing the static current flowing in the object power bus and the value of the static current flowing in the common bus, the calculated difference is compared with the reference value, which. swarm - determined by the formula 1pv. “H-.1 where & 1POT „x1 is the difference of the currents flowing in the power bus 2Q. and the common bus when the diagnostics object outputs are turned off and the j-th input action4, N is the number of basic test elements (BLED) of TTL devices 6, whose inputs are the inputs of the diagnostic object J a is a proportionality coefficient, numerically equal to the value of the input current of one BLA with zero input effect, the value of the logical signal at the input of the 1st BLA, and the logical signals can take values from basis Ј0,11, and according to the magnitude of the mismatch between the actual value of the current difference and its reference value, 5 is defined of the diagnosed object to the healthy or one of the faulty states, at the second stage, the health of the outputs of the diagnostics object is determined, the outputs are connected to the load, the static component of the current consumption of the object flowing in the common bus is measured, the difference is calculated The measured values of the static consumption currents flowing in the power bus and the common bus compare the value of the resulting current difference with the reference value, which is calculated by the formula 0 x ,,,. Gz W.j de u lnoif No J .j4 k-chЈ 1 - "; 5, “SO. the difference between the values of the currents flowing in the power bus to the common bus of the object under diagnosis at the jth input action; z is the value of the logic signal at the i-th output of the logic device at the j-th input action in the basis {0,1}; n is the number of outputs of the object being diagnosed; 1 five a- - proportionality factor, numerically equal to the output current at zero output signal; To - the number of BLA, the inputs of which are connected to the i-th output of the diagnosed object, and according to the magnitude of the difference between the actual and reference values of the difference of the currents flowing in the power bus and the common bus, determine the operability of the outputs of the object being diagnosed. Iffom.u / l + tJnum Cerebral palsy 0t. $ Y I - y / y