303
1 INTRODUCTION
Today, digital and computer technology is present
andparticipatesinthe work of virtuallyany service
onboardamoderntransportvessel.Attheverytop
(intheshipʹscontrolcenter)‐onthenavigationbridge
‐ the work of the navigator is almost completely
provided by digital
electronic equipment. For this,
special professionally oriented integrated bridge
systems[1]areorganized,combiningthemainradio‐
electronicmeansofnavigation.
SufficeittomentiontheECDISelectroniccards[2,
3]. In the energy center of the ship‐in the engine
room‐computerequipmenthascompletelychanged
theorganizationof
watchkeepingforshipmechanics
[4]andelectricians.Thereiselectronicequipmentthat
isrelevanttoabsolutelyallcrewmembers,regardless
of their professional orientation, for example, an
emergencybeacon,radarorradartransponderbeacon
(AutomaticRadarPlottingAid‐ARPA)[5,6].
Fortheoperation,maintenanceandkeepofallthis
electronic
equipment in good working condition
directlyonboardtheship,theInternationalMaritime
Organization(IMO)byitsconventionforthetraining,
watchkeepingandcertificationofseafarers‐“STCW”‐
provides for a special position of an officer in staff:
shipradioelectronics1‐stor2‐ndclass[7].
However, this vacancy
actually exists only on a
limited type of sea vessels, such as large passenger
liners.Onothertransportships,inordernottospend
moneyontrifles tocallonshore specialists,thecrew
members on board try to take on the functions of
maintainingthe operability, maintenance, restoration
andcurrentrepair
ofdigitalelectronicandcomputer
equipment.
The methodology of diagnostics and
troubleshooting of digital electronic equipment
proposedinthearticleisintendedtohelptheminthis
task.This isaspecific workingtoolforanelectronic
engineer(evenforanon‐professional).
Therecommendationsarebasedonmanyyears
of
practical experience of the authors in the work on
diagnostics and adjustment of digital electronic
equipment[8].
2 MAIN
Moderninformationcontrolcomputerandelectronic
systems are certainly more complex than systems of
previous generations. And often the complexity of
softwareandcircuitrysolutionsleadstothefactthat
engineers
operating such systems consider all the
problems associated with their debugging to be the
Diagnostics and Troubleshooting of Ships Digital
Electronics Systems
S.Mikhailov,A.Veretennik&I.Kulyeshov
NationalUniversity“OdessaMaritimeAcademy”,Odessa,Ukraine
ABSTRACT:Algorithmsandproceduresofdigitalinformationsystemstesting,adjustmentandsustainable.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 18
Number 2
June 2024
DOI:10.12716/1001.18.02.05
304
samedifficult.Asaresult,simplesolutionsofvarious
set‐upproblemsbecomeunnoticed.
Therefore, a methodology (basic engineering
algorithm) of troubleshooting and setting up digital
devicesatthesystemlevelisproposed,anditssteps
arecalledʺTenrulesfordebuggingʺ.TheTenRulesis
a practical, systematic
tool for solving some of the
most common problems associated with the
development and operation of information control
computerelectronicsystems.
Theseprinciplesapplytotroubleshootingofwide
varietyofcircuitboardtypes,suchasdigitaloranalog
circuitry, power supply and mixed hybrid integral
circuits.
The use of these
principles when debugging a
failed system will simplify the problem of solving
process and ensure the operability and
commissioning of the system as soon as possible.
Knowledge of these methods is important on all
stages of professional height of specialist on
informationtechnologies:fromtheprimaryeducating
tothesubsequentin
‐planttrainingandperfection[9].
3 RESEARCHRESULTS
Theeffectivenessofthesetencommandmentscanbe
demonstratedbytheexampleofsolvingtheproblems
of certain digital system debugging (Figure 1). Here
wetakea“typical”digitalsystemasamodel[10].The
presented digital printed circuit board is a
part of a
larger system that includes other functional units,
such as power supply, digital interface, data
conversioninterface(analog‐to‐digital and digital‐to‐
analog converters), and an interface section
generatingindigitalformthesignalsthatcomefrom
externalequipment.Inthiscase,weassumethatthe
boardbeing
debuggedistheʺbrainʺthatcontrolsthe
rest of the components of the electronicsystemas a
whole.
Figure1Objectsofanalysisofthedigitalpartofthesystem:
PS‐power supply; DP‐digital part of the system; AP‐
analogpartofthesystem;MP‐microprocessor;SD‐storage
device;DIP‐digitalinterfacepartofthesystem
The main components of the board are the
following: microprocessor, local memory (both
operational, on static storage devices with random
access (RAM), and non‐volatile, on reprogrammable
read‐only memory (EPROM)), an intelligent
peripheral device (requiring minimal participation
from the main processor to implement its own
functions),aparallelbusinterface,andanapplication‐
specificintegratedcircuit(IC)suchasagatearrayor
programmable logic array (PLA), depending on
circuit complexity and speed requirements. In
addition to integrated circuits, additional sources of
possiblemalfunctionscanbediscreteelementsonthe
board‐resistors,capacitorsandconnectors.
Theaforesaiddigitalcardis
usedtocontrolother
cardsinthesystem,interactingwiththemviaparallel
bus interface. In this example, an intelligent
peripheralisaserialdatabusportthroughwhichan
electronicsystemcancommunicatewithothersimilar
systems that form an entire computer network. A
microprocessor located on the board controls
the
transmissionofallinternalandexternalmessagesand
determines the information that must be requested
fromotherboardsorsystemsonthenetwork.
In addition, the processor performs local
computingfunctions.
What should be the first step in the process of
debugging such device? To turn on the power
and
hopeforthebest?Notlikethatinanycase!
3.1 RuleI:Conductavisualinspectionoftheboard.
Theinspectionconsistsofseveralsteps:
1. match the layout drawings of the board with the
real product; make sure all parts are installed
correctly;
2. check that none of
the components was damaged
duringinstallation, reviewalltheIC and discrete
component pins, the quality of the IC panel, and
thequalityoftherations;
3. matchtherealboardwiththeschemeandwiththe
list of elements to make sure that the devices
provided for the scheme
are installed. If a
discrepancy is found, you should refer to the
passportdataorreferencebooktomakesurethat
thereplacementisacceptable;
4. check the values and tolerances of all capacitors
andresistors.
3.2 RuleII:checktheelementsconnections.
Severalimportantchecks:
1. make sure that there
is no short circuit between
power and ground. Many boards have several
supply voltages (for example, 5V, 12V, etc.) and
they can have several independent common
ʺgroundʺ buses (for example,theʺgroundʺ of the
digitalpartofthesystemandtheanalogpartcan
be different and have a difference
in potentials).
There must be no short circuit between all
ʺgroundsʺandpowercircuits;
2. check the wiring diagram of the board for
compliance with the wiring diagram. The circuit
should be called for continuity from the final
output on the connector to the output of each
component(andnot
tosomeintermediatecontrol
point!);
305
3. checkthecorrectwiringofthesyncsignalcircuits
fromtheconnectortoeachcomponentwherethis
syncsignalisused;
4. check the circuits from the final contact of the
connector to the corresponding contacts of the
panelforinstallingthemicrocircuit.
3.3 RuleIII:checkthe
basicparametersofthesystem.
After fulfilling the first two commandments, you
shouldcontrolallthemainparametersofthesystem
level:
1. check theamplitude andnoiselevel of the power
supply, set the voltage rating according to the
circuit requirements. If the noise (ripple) of the
supplyvoltageis
large,youshouldtrytoreduceit
by switching on decoupling and smoothing filter
capacitorsorbyothermeans;
2. configurethecurrentlimitercircuit‐powersupply
protection to make it work at a certain level of
currentconsumption(thankstothis,onecanhope
that the components will not
burn out in case of
unexpectedproblems);
3. check the frequency and duty cycle of the system
clockifitisgeneratedoutsidetheboard.
3.4 RuleIV:checktheproblemnodeforcompliancewith
thecircuitdiagram.
To fulfill this commandment, you should undertake
thefollowingsteps:
1. supply power
to the board. Monitor the current
consumed.Turnoffthepowerandcheckthefirst
threecommandmentsincaseitistoohuge;
2. run the board tests. These tests or verification
procedures allow you to determine quickly
whethertheboardmatchesitselectricalcircuit(i.e.,
whether all components are
functioning,whether
alltracesandthrough‐holesfordouble‐sidedand
multilayer boards are intact, and whether all
signals from the connector pins are correctly
applied);
3. ifthetestfails,thentheproblemmustbecarefully
documented.Recordthenumberofthetestfailed
andallthesignsofsuch
failure.Firstofall,make
sure you are supplying the correct input signals.
Eliminate your own operator errors. Then check
forcorrectinstallation.
Let’s suppose, for example, that a test should
verifythefunctioningoffourdiscreteinstruments.It
providesforthesupplyofsettingsignals to discrete
devices No.
1, No. 2, No. 3 and No. 4 and reading
results01,02,03and04ontheindicator.Yourunthe
testandsendsignalstothefirstinstrument.Yousee
02 instead of 01 on the display. Record your results
andcontinue.Whenyouapplythereferencesignalto
the second discrete device, you notice that 01 is
indicatedonthedisplay.Recordtheresultsagainand
continue. By giving signals to the third and fourth
device,youseethecorrectdisplayreadings‐03and
04,respectively.Thequestionarises:ʺForwhatreason
doesthefirstdiscretedevicelook
likethesecond,and
viceversa?ʺ
First of all, make sure that you are making the
correct input signals. Operator errors should be
eliminatedassoonaspossible.Thencheckforcorrect
installation. The circuit from the controlled discrete
devicetotheindicatormayberoutedincorrectly(for
example, two signals
are mixed up). Maybe discrete
device number 2 is associated with the least
significantbitoftheindicator,orviceversa?Ifweare
talkingaboutawiredbreadboard,thentheerrorcan
beeliminatedimmediately.Ifyouareworkingwitha
printed circuit board, you can either clear the
error
first, or skip the entire test to check the rest of the
board.However,youmustclearlyfixeachproblemso
that you know exactly under what circumstances it
occurredandwhataretheevidences.
Letʹs give one more example of the scheme
implementation.Youhavejustreceiveda
volumetric
wiringboardforsetup. After visuallyinspectingthe
board, checking the integrity of the connections and
settingthebasic systemparameters, youturnonthe
power‐and suddenly you smell smoke. What is
burning?Moreimportantly,whatisthereason?Turn
off the power, repeat the first commandment and
visually check the board. If you can not notice
anything,trytocheckseveralcircuits.Thiswillallow
you to understand which conductor or element has
burned out.The fulfilledcheckingmay indicatethat
thelinefromtheconnectorpowerpinstotheboardis
broken. If so, you should check
whether too small
conductorsize was mistakenlychosenforthe power
wiring.
3.5 RuleV:“separateandpowerer!”
Debuggingcomplexsystemsusuallyrequiretosolve
complex problems, but many of them are easily
solved by breaking them down into several simple
ones,i.e.usuallytheyusethemethodwiththe
name
“divideandrule”.
Tofulfillthiscommandment,followthenextsteps
1. identifytheproblemcorrectly;
2. isolatethesuspiciouspartofthemicrocircuitfrom
therestoftheparts.
Isolationmakesitpossibletoobserveandcontrol
the input reference signals and check the output
signals. This approach allows
you to resolve such
problems as conflicts (race) on the common bus,
problemswiththeloadofIn/Outcircuits,andothers.
Example1.Conflictsituationonthebus[3].
Itoccurswhenseveraluserssimultaneouslytryto
seize the right to control the bus. To solve this
problem,
youshould:
Disconnectalldevicesfromthesystembus,except
for those suspected of creating conflict situation, in
thissituationsuchdevicesastransceiversandbuffers
shall be removed from the board. You should not
expect that isolation will be ensured by using IC
selection circuits (at the CS input) or
at the output
enablinginputfortri‐steadystatelogic.These control
circuits can lead to malfunction and allow access to
thesystembuswhennotprovided.Aftersecuringthe
isolation,checkthereadingandwritingoperationsfor
the devices suspected, with a time‐lapse analysis of
thesignalsdriving
theseoperations.
Example 2. Problems of loading input/output (I/O)
circuits.Theyarisewhenaparticularoutputcircuitis
306
unabletohandlethesystem’sload.Thereareusually
tworeasonsforthis:
1. insufficient levels of logic signals that are out of
tolerance;
2. excessive durations of the leading and trailing
edgesofthepulses.
Isolation provides the opportunity to observe
unloadedoutputsignals.Iftheyarenormal,then
their
distortionisassociatedwithexcessiveloading.
Example 3: Specialized integrated circuit receives
invalid data from a memory device (no bus conflict
occurs).
Inthiscase,variousmemoryaccesscontrolsignals
(egwriteenable,ICselect,outputenable,etc.)should
be isolated; analysis by comparing signals without
loadandwith
loadforthelevelsoflogicalzeroand
one,surges/dipsandthesteepnessoftheleadingand
trailingedgesoflogicalpulsesshallbeprovided.
Thepoint«divideandrule»leadsyoutofocusing
on debugging small sections of the system. This
preventsthetemptationtobelievethatthe
chipsand
other semiconductor elements located on the board
are inoperative and need to be replaced. Such force
methods such as replacing board or system
components are highly ineffective and often fail to
identifyrealsystemproblems.
3.6 RuleVI:Understandhowboardelementsshouldwork
Many debugging problems arise
because the
computerengineersimply does notunderstandhow
the electronic components used in the system are
supposed to work. This is not only about the clean
functioningofthedevices,butalsoabouttheelectrical
characteristics for direct and alternating current.
Various problems can manifest themselves at the
system level,
even if all the devices on board are
functioning. These can be problems with the
performanceoftheboardasawhole,thecorrectness
oftheinputinformation,theintegrityofthedataand
the required time sequence for the arrival of
information‐andallofthemcanbeboth
permanent
and episodic, intermittent. Moreover, problems can
occur in the device as a whole, even if individual
componentsoftheboardarefunctioningnormally.
Theprocedureincludesthefollowingsequenceof
actions:
1. it is necessary to take into account the electrical
characteristicsoftheDCcircuits;
2. identify unused inputs
that are not connected
anywhere (ʺfloatingʺ andʺhanging in the airʺ
inputs).Thewaytoeliminatesuchmalfunctionsis
tofixthelogiclevelsbyinstallingloadresistorson
suchinputs;
3. it is necessary to take into account the type of
output circuit when checking the output signals.
There are three options (Figure 2): U‐out‐max
(logic levelʺ1ʺ), U‐out‐min (logic levelʺ0ʺ) and
ʺthirdstateʺ‐highimpedance.
Figure2.PossiblelevelsofoutputsignalsofdigitalICs
Itisnecessarytofindoutthetypeoflogicalsignals
inthedevice‐ʺpositiveʺorʺnegativeʺlogic,thevalues
of the logical levelsʺ1 ʺ andʺ0ʺ for it, as well as the
permissiblevaluesoffluctuationsofthesevalues.
Manysystemproblemsaretheresultofnottaking
into account
the electrical characteristics of the DC
input circuits, or unused inputs not connected
anywhere (so calledʺfloatingʺ orʺsuspended in airʺ
inputs). The output circuit must create the required
voltage levels of logical zero and one for all inputs
connectedtoit.Youshoulddoublecheckthevoltage
requirementsfor
allICsintheproblematicorisolated
specializedsectionoftheboard.
Floating inputs are board inputs that do not
receivevoltageorcurrentsettingsignalsfromoneor
anotheroutput.Theseinputscancausefunctionaland
parametricproblemsinthesystem,suchasincreased
current consumption, increased noise, and
unexpected
or unwanted generation of logic control
signals as a result of unwanted or unexpected
malfunctions.Duringdebugging,checkthatallinputs
receive either dynamic or constant static reference
signals.Onlyinputswithleakageorloadresistorscan
beleftwithoutsuchsignals.
When checking the output signals, the type of
output circuit must be considered. Active output
circuitscreatevoltagefor inputs:high‐forthelogic
levelʺ1ʺ or low‐for the logic levelʺ0ʺ. Three‐state
outputscreatevoltagesfortheinputs:highorlow,or
a third, high‐impedance, state. Open‐drain or open‐
collectoroutputscreateonly
voltagefortheinput‐a
highlevel.Intheabsenceofanactivesignalatsuchan
output,ahigh‐impedancestate.
Inorderforanopencollector/draintri‐stateoutput
circuittoproperlydrivetheinput,itrequiresadrain
orloadresistor.Intheabsenceofsucha
resistor,the
outputcircuitry,whenitgoesintoahighimpedance
state,essentiallycausestheinput“tofloat”.Checkall
inputs to the circuit to determine if a drain or load
resistorisrequiredhere.Youalsoshouldremembered
that the resistance of the resistor and the current
capabilitiesofthe
outputbufferaffectthedurationof
the rising and falling (leading and trailing) edges of
theoutputsignal.
4. analyze the logical formulas describing the
functioningoftheelementsintheboard;
5. checktheconfigurationofthedevices.
Since most of the elements are programmable
(RAM, ROM, MP, PLM,
BMK, MS, DC), incorrect
settingoftheirconfigurationcreatesproblemsforthe
operationofthedeviceasawhole.
Itisnecessarynotonlytotakeintoconsideration
the input and output characteristics of all
microcircuitsinthesystem,butalsotounderstandthe
functioning of semiconductor devices such as PML
(programmable matrix logic) and specialized ICs.
When debugging the system, you should re‐analyze
the logical formulas describing the functionality of
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thesemicrocircuits.Itoftenhappensthatanerrorina
logicalformulawillrequiremanyhoursofsetupwork
to correct it. For example, a PML programmed to
implement bus arbiter functions may from time to
timegrantbusaccesstomorethanoneDMAdevice.
Thereasonof
suchaproblem canonlybe identified
by a careful analysis of the logical formulas of the
PMLusingthe“divideandrule”methodology.
3.7 RuleVII:Understandhowsoftwareissupposedto
work.
To fulfill this commandment, use the following
guidelines:
1. interactionsbetweenhardwareandsoftwareoften
cause many
system‐level failures and problems.
The key to effectively debugging such systems is
understanding of how software affects the
hardware;
2. checkthattheconfigurationsoftwaretobeworking
correctly;
3. analyze the interaction of hardware and software.
The hardware operability check is usually
performed by writing (issuing) data to
a device
withthefollowingreadingforthisdevice;
4. the best way to debug for complicated systems,
complicatedsoftwareandhardwaresystems,isto
simplify the software. This approach is
conceptually similar to the method of isolating
individualdevicenodes.
Letʹs start with the main question:ʺHow does
software
affect hardware?ʺ In this example of a
tunable system (Figure 1), a programmable
microprocessor controls the configuration and
operation of the ASIC and intelligent peripheral
device. When debugging the system, verify that the
configurationsoftwareisworkingcorrectly.Thenyou
need to analyze the interaction of hardware and
software.If
atthehardwarelevelincorrecttransferof
information to system devices takes place, then
problems usually arise. A simple hardware check is
usuallydonebywriting(outputting)datatoadevice
andthenreadingitforthatdevice.
Thismethodofdebuggingbyperformingstepwise
read / write operations allows you
to identify
effectivelycertainhardwarelimitationsofthesystem.
Failuretoreadcorrectlythedatawrittentothedevice
willconfirmthepresenceofproblemssuchasaccess
toodd/evenaddressesorwordlength.
Problems of access to odd/even addresses arise
when the microprocessor and software provide for
recording only
by odd or only by even words (for
example,1,3,5,etc.),andsystemdevicesrequireboth
oddandevenaddresses.Wordlengthproblemsarise
when the software and circuitry of the system
requiresdifferentwordlengths.Allsuchproblems,if
identifiedinatimelymanner,canbeeasilyresolved.
3.8 RuleVIII:Understandhowtestfacilitiesaresupposed
towork.
Thiscommandmentreferstothesetupprocess,when
the last enters the stage of testing the board or the
complete system. Here you have to deal with
problemsrelatedtotestequipmentandtestsoftware:
1. determinethenecessity
ofthistest;
2. interpret correctly the research results, identify
incorrecttestingmethods;
3. analyzetheproblemandclassifyit,referringtothe
category of functional or parametric. When it
comes to parametric problems, the measuring
instruments used, such as test loads and
measuring instruments, should be evaluated.
Analysis of functional
problems consists in
comparingtestmodes with real modes of system
operation.
At this stage of testing, it is determined whether
thetestoperationscorrespondtotherealcapabilities
ofthesystem.Manyfunctionalproblemsarisewhen
testprogramsdonottestallmodesandmeansofthe
systemor
boardthatcorrespondtotherealoperating
conditions. These problems can usually be solved
whenthesystemorboardperformscertainoperations
andthemethodsusedtocontroltheseoperationsare
analyzed.
3.9 RuleIX:Donʹtʺgethungupʺ‐takebreaks.
For this commandment, it is necessary to follow the
presentrecommendations:
1. when you work on complex problems, you are
forced to concentrate completely on it and,
unfortunately,youfocusononeproblemarea.The
breakallowsyoutoopenyoureyesandseeother
possiblecausesofthemalfunction;
2. takingabreakwillhelpyougetout
ofstress.
Atimelybreakcanoftenbeveryuseful.Ifyouare
ʺobsessedʺ,youcan just haveacupof coffee, takea
ʺstretchʺorgetagoodnightʹssleep.
Whytakebreaks?First,whenyouareworkingon
difficultproblems, youhaveto concentrateyourfull
attentiononthem.Unfortunately,itmayturnoutthat
youareonlyfocusingononeproblemarea.Abreakin
operation allows you to see other possible causes of
theobservedabnormalities.Takingabreakisawayto
removeblindersandsolveaproblem.
Second, if you have been
trying to solve a
particular serious problem for a long time, youmay
findyourselftoomuchstressed.Donotpanic.Takea
break,checkthefulfillmentofcommandmentsfromI
to VIII. By repeating this systematic procedure for
debugging your board, you may find important
ʺpointsʺthatyousimply
didnotnoticebefore.
3.10 RuleX:Trytolookattheproblemfromanew
perspective.
You have fulfilled the commandments from I to IX,
but you could not find the cause of the disfunction
and understand any systemic problems. What to do
next? Invite someone from your colleagues who
can
help you to look at the problems from a new
perspective‐someone who is not familiar enough
with your board and its construction, but can ask a
number of fundamental questions, i.e. have a fresh
viewontheproblem.
The important thing to remember in this rule is
that
CommandmentXisabouttakingafreshlookat
yourtask,andnotaboutaskingtoomuchhelp. You
308
can just get confused if you have too many helpers
and advisors. Be selective inviting colleagues to
participate in the setup process. Ask for help from
thoseexperts,whoseanalyticalmind,experienceand
opinionyouvalue.Thenyourrequestforhelpwillbe
beneficialandwillnotinfluenceyourcredibility.
4 CONCLUSIONS
Algorithms and procedures of digital information
systems testing, adjustmentand sustainable, integral
and complex estimation of refuse of the digital
informative system, both «from within» her and
«outside»,gives an opportunity to define reasons of
refuse and find the ways of renewal of the system
[11]. The described
methodology of search of
disrepairs in the digital systems is a quite good
workinginstrumentfortheseaims.
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