The possibility of improving on attributes of a solution which are traditionally opposed each other is proved. For digital components of safetyrelated systems, the method of improving on attributes of a checkability of the circuit and trustworthiness of the results calculated on FPGA with the LUToriented architecture is offered. The method is directed to improving of the ready project by a choice of the version of a program code without change of the hardware decision. Versions of LUT memory programming and a set of faults on which these versions exert impact are generated. Faults of shorts between adjacent address inputs of LUT are considered. Operation of the circuit is simulated on all versions and on all set of faults. The method selects the versions providing increase in a checkability of the circuit in a normal mode and trustworthiness of results in emergency mode of the safety-related systems.
Objects of the increased risk in power engineering, on transport and other areas became
natural surroundings of the human. Power stations and the high-speed railroad, aircraft
permanently increase complexity and capacities. It requires the appropriate
enhancement of the safety-related systems ensuring the functional safety of these objects [
We offer a method for improving the digital components of safety-related systems
in two attributes important for the functional safety: checkability of the circuit and
trustworthiness of results. The insufficient checkability of the circuit restricts
possibilities of on-line testing to detect faults in the course of computation. This creates a
problem of the hidden faults in safety-related systems [
Such opposition of these and other attributes is perceived as a norm, however it
has no objective character, and it is only result of limitation of our models, i.e. our ideas
concerning the nature of objects of a research. A certain step in development of models
can be taken, using resource-based approach [
One of fuzziness forms is redundancy shown in a set of versions of a solution. Such
diversity is supported by design of digital circuits on a programmable logic which removes a
contradiction between universality and specialization of an circuit element basis: the
universalization is provided with stamping of chips, and specialization – programming of
their functions [
Basic ideas of a method are described in section 2. The possibility of elimination of a traditional contradiction between a checkability of the circuit and trustworthiness of the results calculated by this circuit is considered. Influence of versions on faults of shorts between adjacent address inputs of LUT is analyzed. An opportunity and feasibility of the maximum distinguishing of attributes of a circuit checkability and trustworthiness of the results is shown. Program implementation of a method is provided in section 3. Basic data and steps of the program execution including simulation of operation of the circuit are defined. The results of simulation allowing to select the version of the circuit programming are shown in the form of the table. 2
The main position of the offered method is the possibility of elimination of a
traditional contradiction between a checkability of the circuit and trustworthiness of the
results calculated by this circuit. In other words, the method is based on a possibility
of development of the methods with multiple effect [
Responses to these questions should be looked for in consciousness of the human.
His limited models restrict our opportunities. The human thinks by exact data, i.e.
integers by the nature. These are numbered data. In the consciousness the human creates a
set of any objects and numbers its elements with abstracting from the features
distinguishing real objects. It promotes perception of the natural world at the level of
replication where the method of the “Robbing Peter to pay Paul” dominates. The modern
computer world, generally is at this bottom level of development – replication. Array
structures in computer systems and their hardware components are stamped using identical
operational elements. Software modules are also stamped for the purpose of their
connection to different applications [
At the same time, the natural world doesn't create anything identical, and even stamping generates versions, i.e. higher level of diversification in resources development is implemented. In particular, the increase in trustworthiness based on the double account or use of majority systems is reached not due to stamping of the duplicating elements, and thanks to their not identity, i.e. version redundancy. Systems of critical application are development of computer systems with diversification of an operating mode by its division on normal and emergency.
Substitution in our consciousness of actual level of diversification on the level of replication distorts perception of methods of resources development: methods with the multiple effect are perceived one-sidedly as methods of the “Robbing Peter to pay Paul”, tabooing overcoming traditional contradictions between attributes of the problem solution. Being in the real natural world, the human can't but develop methods of the multiple effect, but does it unconsciously and uses their results partially or blindly, without guessing this use. The way to use of methods with the multiple effect lies through diversification, i.e. distinguishing of versions.
Diversification of an operating mode of safety-related systems by its division into normal and emergency allows to diversify requirements to a checkability of the circuit and trustworthiness of results in relation to the normal and emergency mode. The checkability of the circuit shall be maximum and minimum respectively in normal and emergency modes. In a normal mode it provides the best conditions for fault detection with methods of on-line testing, and in emergency mode it restricts action of faults. Trustworthiness of results shall be minimum and maximum respectively in normal and emergency modes. Low trustworthiness of results in a normal mode accompanies online testing in detection of faults which are found by identification of non-authentic results. High trustworthiness of results is an important condition of successful actions in an emergency mode of safety-related system. Thus, opposition of a checkability of the circuit and trustworthiness of results changes at the level of diversification on their coherence in the direction of support in the functional safety of safety-related systems.
The following position of a method is aimed at the maximum distinction of
attributes of a checkability of the circuit and trustworthiness of results in order to direct of
them to opposite extremal values. This position is based on use of versions in a
program code for the LUT-oriented architecture of FPGA projects and versions in
manifestation of faults like shorts. Creation of versions in a program code for the
LUToriented architecture of FPGA projects was considered in [
In the left of Fig. 1, two versions in programming of pair of LUT 1 and LUT 2 in the conditions of shorts of address inputs D and C of LUT 2 are shown.
In the first version, the LUT 1 and LUT 2 generate functions X = D B and Z = (A B) (C D), respectively. These functions are represented in tables which rows and columns are determined by values of 2-b codes DC and BA, respectively. The direct value of X is calculated at an output of LUT 1 and arrives at a direct address input D of the LUT 2. The signal Y arrives at an input C of the LUT 2 which forms signal Z at an output. The second version calculates the same result Z at the output of LUT 2 by using of functions ¬X and Z* = (A B) (C ¬D), where ¬D = ¬X. Inverse value of X is calculated at an output of LUT 1 and arrives at an inverse address input D of the LUT 2. Inverse of an address input of D is provided with replacement of bits in memory of LUT 2: two top rows of memory bits are interchanged with two bottom rows.
Fault like shorts of adjacent address inputs generates an error in the area designated as P of different values of signals at these inputs and doesn't show an error otherwise, i.e. in the area R where these values match. In the right parts of Fig. 1, a and Fig. 1, b, two versions of the P and R areas are shown. In case of change of the version in programming of LUT pair, the P and R areas are interchanged the position. It is important as in these areas opposite results in relation to support of a checkability of the circuit and trustworthiness will be achieved. In the P area, a checkability of the circuit raises, and trustworthiness of results will be reduced. In the area R, on the contrary, the checkability of the circuit decreases, and trustworthiness of results will be increased. Thus, an opportunity to interchange the position for sets of the P and R areas allows to inscribe better them in sets of input data of the normal and emergency modes, i.e. to raise the circuit checkability in a normal mode and trustworthiness of results in emergency one. 3
The offered method generates a set of versions in programming of LUT and provides a choice of the version which improves a digital component of safety-related system on two attributes: checkability of the circuit and trustworthiness of results.
Program implementation of this method defines all versions of a code of programming for the given hardware implementation of the LUT-oriented architecture of the FPGA project and all faults like shorts on which versions exert impact.
Further in the course of simulation of the circuit operation, the following actions are performed. For each version, the summary amount of the erroneous results received owing to action of each fault is defined. Simulation is executed for each input word. Different areas of the normal and emergency modes are researched: the amount of erratic results is calculated. Versions which as much as possible show errors in the used areas of a normal mode and exclude errors in emergency one are selected.
The demonstration option of program implementation of a method is developed
using Delphi 10 Seattle demo-version [
On a step 1 the table "Versions" in which all possible versions in programming of
the circuit on FRGA are described is built. For each version 1, …, 8, the LUT,
inverting the output are marked by units. Besides, the table "LUT Codes Versions" in which
for LUT 2 of pairs are specified the mask codes allowing to replace value of memory
bits according to need of compensating the inverse values at address inputs is built.
On a step 2 the table "Faults" showing the list of faults depended on versions of
programming is built. The rows of this table contain two elements: number of LUT and
type of faults: A-B, B-C or C-D, i.e. shorts between address inputs of A and B, B and
C or C and D, respectively. On following step “Start”, simulation of the circuit
operation at all input values of an operating mode for all versions of programming and all
set of faults is executed. After simulation the threshold separating the normal and
emergency mode is set and the table "Results" which shows quantity N and E of
errors appearing respectively in normal and emergency operation and also their amount
N + E and a difference N – E is created. Results of simulation show that version 1
contains identical quantity of errors (14) in both modes. Version 2 provides the best
value of checkability (19 errors) in a normal mode. Version 6 provides the best
trustworthiness (0 errors) in emergency mode with an average value of checkability (12
errors).Version 6 is preferable in case of use in normal and emergency mode of the
same version of the circuit programming. Functioning of the circuit can be ensured with
use of different versions in normal and emergency mode [
The method for improving of a checkability of the circuit and trustworthiness of results in digital components of safety-related systems is offered. The digital components developed on FPGA with the LUT-oriented architecture are considered. The method allows to detect better faults of digital circuits in a normal mode and to reduce activity of faults in emergency mode of system operation. Thus, the method increases the functional safety of safety-related systems and the objects of the increased risk controlled by them. At the same time, not only the method, but also questions of its development are important. How this method was received? What objective conditions shall develop for development of this method?
The method improves two attributes which are traditionally opposed each other. The high checkability of the circuit allows to detect timely permanent faults, but promotes hyperactivity of the transient faults reducing trustworthiness of results. Overcoming negative effect of such opposition of attributes became possible in safetyrelated systems as a result of diversification of an operating mode by its division on normal and emergency. It led to diversification of the input data and requirements imposed to a checkability of the circuit and trustworthiness of results. Opposition of two attributes became the useful to support of the functional safety of safety-related systems.
However, this opposition shall be opposite for the normal and emergency modes where checkability and trustworthiness shall dominate respectively. Faults diversify input data by their division into two sets defining the correct and erroneous result. However this diversification doesn't correlate with diversification of input data for the normal and emergency modes. Coordination of these diversifications became possible with development of integrated circuits with a programmable logic. Version redundancy of the program code in FPGA projects has completed the formation of objective conditions for development of the offered method providing a choice of versions for domination of a checkability in a normal mode, and trustworthiness – in emergency mode.
Thus, development of offered method became possible as a result of development of resources – models, methods and means – at the level of diversification.