Note: Descriptions are shown in the official language in which they were submitted.
3~16
CONl~IGURATION MODULE F~R AVIONIG~;
SIGNAL PROCESSIN~ UNl~;
Technical Field
In general, this invention relates to methods and apparatus for
5 configuring signal processing apparatus for oper~tion with input and output
devices of various types and configuration. Although the invention has utility in
various types of electrical and electronic systems, in its preferred form, it isparticularly suited for configuring the signal processing unit of an avionics
system for operation with signal sources and signal utilization devices that can0 alternatively be employed within that particular avionics system.
Background of the Invention
Advances in the digital signal processing arts have made it possible
to reali~e a wide range of electrical and electronic apparQtus by utilizing a
programmed digital signal processing unit in combination with vQrious types of
15 signal sources and signal utilization devices. In some such systems3 it is
necessary that the programmed digital signal processing unit be capable of
operating in conjunction with alternative signal sources and/or alternative signal
utilization devices that exhibit disparate signal characteristics. This require-ment can be brought about for many reasons, including preferences of the system
20 user or to facilitate the use of existing signal sources and utilization devices that
serve as components of another electrical or electronic system that is installedat the same location or facility. In cases in which a substantial number of
alternative signal sources or signal utilization devices must be accommodated
and there is disparity between signals supplied by the signal sources and/or
25 disparity between the signals required by the signa~ utilizQtion devices, theproblem of configuring the signal processing unit for operation with the
alternative components can be substantial.
The problem of accommodating various signal sources and signal
utilization devices has become especially troublesome with respect to signal
30 processing units that are utilized in avionics systems of the type employed in
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commercial aircraft. In this regard, the sir carrier or company that operates the
aircraft generally determines what types of avionics systems will be installed on
the various aircraft of that carrier's fleet, and further specifies the configura-
tion of each system, including which particular signal sources and signal
5 utilizstion devices are to be employed. Regardless of whether a particular signal
utilization device is a cockpit display unit, an actuator, or another avionics
system, several alternatives often are available to the carrier. In many cases,
there is substantial disparity between the nature and characteristics of the drive
signals required by the various alternative utilization devices. Moreover, modern
10 transport aircraft include numerous avionics systems and oftentimes the drivesignal required by a selected utilization device can be derived from different
sets of input signals. Such alternative sets of input signals include signals
provided by other avionics systems and signals supplied by various alternative
transducers, sensors nnd actuators. Even further, in addition to the input signals
15 required for deriving the system output signals, certain avionics system signal
processors require input information that modifies or controls the manner in
which the signal processor operates. A wide variety of this type of signal
information can be required. For example, it may be necessary to supply the
signal processor with a signal representing the aircraft identification (i.e., "tail-
20 numbe- ") in situations wherein proper signal processor operation is dependent on
the particular aircraft or type of aircraft. In some situations, even the language
in which fi system displays messages to the flight crew or passengers may be
controlled by supplying a particular, selected signal to the system signal
processor. For all these reasons, there is often substantial disparity between the
25 nature and characteristics of the input signals that are supplied to the signal
processing unit of an avionics system.
To facilitate the needs and desires of various air carriers, the
manufacturers of aircraft and avionics systems have attempted to generically
configure the signal processing unit of various avionics systems in a manner that
30 provides easily selectable options which adapt a particular avionics system to a
specified configuration. Generally speaking, these configuration options are
made available by arranging the signal processing unit so that it is capable of
supplying each type of alternative output signal and is capable of operating with
each alternative input signal. In these arrangements, selection of the desired
35 configuration is effected by alternative interconnection of various circuits and
terminals that are contained in the signal processing unit. More specifically, the
signal processing unit often includes a plurality of terminals tnat are electrically
innerconnected with the signal processing unit circuitry so that innerconnecting
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the various terminals and/or connecting various terminals to a particular
electrical potential (e.g., ground or another specified voltage) configures the
signal processing unit in the desired manner. In effect, in such an arrangement,the signal processing unit is "informed" of the manner in which the avionics
5 system is configured and is adapted to operate with the input and output signals
that are associated with that particular configuration~
In prior art arrangements, the innerconnections that define the
desired configuration have been established in a variety of manners. For
example, in some prior art arrangements, a plurality of switches that determine
10 the operational characteristics of the signal processing unit are provided either
within the signal processing unit or are mounted on the enclosure that houses the
signal processing unit. In this type of arrangement, the switches are set to
provide the desired configuration prior to the time at which the signal processing
unit is installed on the aircraft.
This particular prior art approach presents at least one dis-
advantage or drawback. In particular, the signal processing units of avionics
systems are generally packaged within a housing that slides into a tray that is
mounted in equipment racks. Mating electrical connectors that are mounted on
the tray and the signal processing unit allow rapid removal for service, repair or
20 replacement. Since many carriers operate different types of aircrhft and often
configure a particular type of avionics system differently for the various typesof aircraft, flightline personnel must set the switches of the signal processingunit to configure the unit for that particular type of aircraft and must test the
signal processing unit for proper operation prior to installation. This can result
25 in delays that prevent maximum utilization of the aircraft and disrupt scheduled
departures and arrivals.
In a second prior art approach, which overcomes the above-
discussed replacement problem, each terminal of the signal processing unit that
determines the operational configuration is connected to a pin (or receptacle) of
30 the signal processing unit connector. In this arrangement, the operational
configuration of the signal processing unit is established by electrically inner-
connecting the mating receptacles (or pins) of the connector that is mounted on
the tray that receives the signal processing unit. Although this particular prior
art approach allows the aircraft wiring to define the configuration of the signal
35 processing unit, the number of configuration options that must be accommodated
has increased to the point where this technique is at least somewhat undesirable.
In this regard, the availability of additional avionics systems and components
that provide additional alternative input signals and require additional output
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signaLs has reached the point where it may be necessary that a particular signalprocessing unit provide a large number of configuration options. This means thata large number of electrical connections must be made at the connector that
mates with the signal processing unit. Thus, a large number of connector pins
5 must be dedicated to determining the operational configuration of the signal
processing unit. This means that relatively large connectors must be employed
and a greater amount of labor is required to install the jumpers or straps that
determine the signal processing unit configuration. The result is undesired
increased cost, complexity and weight.
Summary of the Invention
In accordance with this invention, the operating configuration of an
avionics system signal processing unit is established by a memory unit that is
contained in a separately packaged configuration module. Digitally encoded
signals that characterize the desired configuration are stored in the memory unit
15 either prior to initial installation of a signal processing unit or at the time at
which the signal processing unit is installed in the avionics system. Preferably,
signal` codes that define each configuration variable (e.g., the type of signal
sources and signal utilization devices employed by the system and various other
system parameters) are stored in the memory unit in a predetermined sequence.
20 Whenever the signal processing unit is replaced, the codes are supplied to the
newly installed signal processing unit in a digital signal format. Thus, the mating
electrical connectors that electrically innerconnect the signal processing unit
with the remaining components with the avionics system need only include a
small number of connections that are dedicated to configuring the signal
25 processing unit.
In the currently preferred embodiments wherein the signal process-
ing unit employs a programmed digital signal processor, the configuration moduleincludes a serially accessed programmable nonvolatile memory unit and is
mounted to the tray that receives the signal processor unit. In this arrangement,
30 only six electrical connections are required between the signal processing unit
and the configuration module.
In one realization of the currently preferred embodiment of the
invention, the avionics system includes a control and display unit which is
mounted in the crew compartment to facilitate keyboard entry of data and
35 various system commands and to facilitate cathode ray tube display of system
information and instructions. In this arrangement, the signal processing unit isprogrammed to provide a system installation procedure wherein the control and
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display unit is utilized to store the configuration codes in the configuration unit
memory during the initial installation of a signal processing unit.
Additionally, in systems that employ 8 programmed digital signal
processing unit, a signal that is identical to the signal stored in the configuration
S module is read into the nonvolatile memory of the signal processing unit during
the initial installation procedure. This information is compared with the signalstored in the configuration module each time the avionics system is activated
("powered-up"), to verify proper configuration of the signal processing unit andto ensure that no changes have occurred in the signal stored in the configuration
10 module memory unit. Additionally, the configuration information stored in thenonvolatile memory of the signal processing unit serves as a back-up copy of theproper configuration data in the event of configuration module failure or
removal.
8rief Description of the Drawing
These and other aspects and advantages of the invention will be
recognized by reference to the following detailed description of an illustrativeembodiment, taken in conjunction with the drawing, in which:
FIGURE 1 is a block diagram that illustrates an avionics system
wherien the operational configuration of the system signal processing unit is
20 established in accordance with this invention;
FIGURE 2 is a perspective view of a signal processing unit and the
mounting tray that receives the signal processing unit which illustrates a
configuration module mounted to the mounting tray and electrically inner-
connected with the signal processing unit in accordance with the principles of
25 this invention; and
FIGURE 3 is a chart that illustrates the installation procedure for
the embodiment of the invention depicted in PIGURE 1.
Detailed Description
Within reference to FIGURE 1, an avionics system of the type to
30 which this invention primarily relates includes a programmed digital signal
processing unit 12 that is connected to a plurality of signal sources 14 and is
connected to a plurality of signal unit utilization devices 16. In operation, a
central processing unit CPU 18 of the programmed digital signal processing
unit 12 sequentially samples the input signals provided by signal sources 14,
35 processes the received signals and provides output signals to the signal utiliza-
tion devices 16. In the arrangement depicted in FIGURE 1, each signal source 14
supplies data to CPU 18 via an associated input data port 20 that is connected to
CPU 18 by means of an address and data bus 22. In a similar manner9 the output
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signals supplied by CPU 18 are selectively coupled to each of the various signalutilization devices 16 via data bus 22 and an associated output data port 24.
As is known to those skilled in the art, the depicted arrangement of
digital signal processing unit 12, input signal sources 14 and signal utilization
devices 16 typifies a variety of avionics systems of the type that employ signalprocessing. Such avioni~s systems include, for example, navigation systems of
various types and description, various types of communication systems, various
types of flight data recording systems, and various types of performance
monitoring systems. As will be recognized by those skilled in the art, the
configuration and nature of the signal sources 14 and signal utilization devices 16
of FlGURE 1 depend on the particular type of avionics system of interest. For
example, sign~l sources 14 can be various conventional transducers or can be
other avionics systems that are utilized on the aircraft employing the avionics
system of interest. In a similar manner, the signal utilization devices depicted in
FIGURE 1 can be conventional indicators that display information to the night
crew or can be another avionics system which requires a signal supplied by the
avionics system of interest. Further, those skilled in the art will recognize that
avionics systems that are typified by the block diagram of FIGURE 1 can include
components not iliustrated in FIGURE 1. For example, such systems may include
apparatus such as signal acquisition units, digital to analog signal converters and
other apparatus that, in effect, collect or preprocess the signals utilized in that
particular avionics system.
Regardless of the type of avionics system and the particular signal
input and signal output arrangement, those skilled in the art recognize that theCPU 18 of digital signal processing unit 12 includes an arithmetic/logic unit that
is innerconnected with a random access memory (RAM) and a read only memory
(ROM), none of which are shown in FIGURE 1. In operation, the CPU is
programmed by instructions stored in the ROM to sequentially access the data
supplied by the signal sources 14; process the signal data in accordance with
instructions stored in the ROM; and supply output signals to the signal utilization
devices 16 in accordance with additional instructions stored in the ROM. During
these operationsJ the RAM is utilized for temporary storage of calculation data
and to provide various registers that are required for proper sequencing of
CPU 18.
As is indicated in FIGURE 1, some avionics systems include a
control and display unit 26, which serves as an interface between a member of
the flight crew and digital signal processing unit 12. Although various arrange-ments are possible, control and display unit 26 of FIGURE 1 includes a
~Z~3~Li 6
- 7
keyboard 25 (which ~llows data to be transmitted to digital signal processing
Imit 12) and includes a cathode ray tube (or equivalent display) 27 (which permits
the display of various information). As also is indicated in FIGURE 1, such a
control and display unit can be coupled to the bus 22 of digital signal processing
unit 12 by means of a dedicated data port (identified as CDU Data Port 28 in
FIGURE 1). Additionally, in many cases, the digital signal processing unit 12 ofan avionics system includes a power supply 31 for supplying electrical power to
CPU 18 and various other active circuits contained in signal processing unit 12.As previously mentioned, various kinds of signal sources 14 and
signal unit utilization devices 16 are employed in realizing various types of
avionics systems. Moreover, alternative signal sources and signal utilization
devices often are available for a specific type o avionics system. That is, even
though the avionics system of interest may be a particul~r type of navigation
system that provides certain information to the flight crew, the signal utilization
devices may include several alternative types of indicators and/or the navigation
information provided by that specific navigation system may be supplied to
alternative avionics systems. In a like manner, it may be possible to derive therequired navigation information from various alternative signal sources, includ-ing signals provided by various other avionics systems and/or signals provided by
various alternative transducers and sensors. For example, the invenlion dis-
closed and claimed herein is currently employed in a night management
computer, which provides many conventional navigation features and, in addi-
tion, provides additional valuable navigation information. That flight manage-
ment computer includes a large number of serial data ports that functionally
correspond to data ports 20, 24 and 28 of FIGURE 1~ with the data ports being ofvarious types including ARINC 429 serial data ports, RS 422 serial data ports and
serial data ports utilizing other specific protocol. Although the nature and
characteristics of the signals transmitted or received by a large number of the
data ports are identical in each installation of the flight management computer,options must be provided relative to a certain number of the data ports so as toaccommodate the various optional, alternative signal utilization devices and
signal sources. In this regard, in the current flight management computer
realization of the invention, four input ports are available for supplying aircraft
position signals to the flight management computer with there being three
optional signal sources available for each of these data ports. In addition, eight
radio-tuned ports are provided for receiving various alternative signal informa-tion and various fuel flow rate signals can be provided to any or all of four fuel
flow rate ports. Further, there are numerous data ports wherein an option exists
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as to connection to one of two alternative signal sources or signal utilization
devices.
In accordance with the present invention, configuring digital signal
processing unit 12 for operation with the various possible sets of alternative
signsl sources and signal utilization devices is accommodated by a configurationmodule 30. As is indicated in FlGURE 1, the configuration module 30 includes a
configuration memory 32 which is innerconnected with a programmable data
port 34 of signal processing unit 12. In operation, CPU 18 of digital sign~l
processing unit 12 is programmed to accommodate each of the optional sets of
signal sources and signal utiliz~tion devices. A digital signal which representsthe desired configuration (e.g., the selected alternative signal sources and signal
utilization devices) is stored in configuration memory 32 either prior to or at the
time of system installation. Each time the avionics system is subsequently
activated, CPU 18 accesses the data stored in configuration memory 32. This
information is utilized to configure digital signal processing unit 12 so that
CPU 18 selectively executes signal processing appropriate to the signPl sources
and sign~l utilization devices being employed by the avionics system.
In accordance with the invention, and as is indicated in FIGURES 1
and 2, digital sign~l processing unit 12 and configuration memory unit 32 are
separately packaged and mounted. More specifically, in the arrangement of
FIGURE 2, digital sign~l processing unit 12 is contained in a standard avionics
enclosure 34, which slides into a tray 36. In most installations, tray 36 is
mounted in a rack (not shown in FIGURE 2) that receives various other electricaland electronic equipment carried by the aircraft. Regardless of the manner in
which tray 36 is mounted, configuration module 30 of the illustrated arrange-
ment is mounted to the upper surface of Q bracket assembly 38, which extends
upwardly from the rear portion of tray 36. As the avionics enclosure 34 is slid
rearwardly into rack 36, a connector 40 (which is mounted on a forward face of
bracket 3~), engages with a mating connector of the avionics enclosure (not
shown in FIGURE 2). The electrical connections provided by connector 40 and
the mating connector of avionics enclosure 34 provide electrical connection
between digital signal processing unit 12 and configuration memory unit 32, the
signal sources 14, the signal utilization devices 16, and control and display
unit 26.
As is indicated in FlGURE 1, relatively few electrical connections
are required between configuration memory 32 and digital signal processing
unit 12, even though numerous options are specified by the data stored in
configuration memory 32. For example, the configuration module 30 that is used
~L2431~6
in conjunction with the previously mentioned flight management computer,
utilizes a type NMC9306/COP 494, serially programmable nonvolatile memory,
which is commercially available from National Semiconductor Corporation of
Santa Clara, California, as configuration memory 32. In this realization of the
5 invention, only six electrical connections are required between configuration
module 30 and digital signal processing unit 12. As is indicated in FIGURE 1,
two of the required connections couple operating potential (Vcc and system
ground) from power supply 31 of digital signal processing unit 12 to configuration
module 30. Two of the remaining electrical connections serve as data input and
10 data output connections to configuration memory 32. Clock signals are coupledfrom digital signal processing unit 12 to configuration memory 32 via one of theremaining electrical connections and the final electrical connection is used in
conjunction with the clock and data input conections to select and control the
operation of configuration memory 32 (i.e., write input data into memory, read
15 data from memory, or erase a specified portion of memory).
Both the structure and operation of the invention can be further
understood with reference to the proecedure employed in the currently employed
embodiments of the invention relative to initially establishing the operational
configuration of programmed signal processing unit 12. In this regard, in the
20 previously mentioned flight management computer that employs the invention,
one example of a utilization device that is subject to various alternatives or
options is the system Horizon Situation Indicator. As is known in the avionics
art, the Horizon Situation Indicator displays information including the aircraftheading and the aircraft bearing. As is further known in the art, several
25 alternative types of Horizontal Situation Indicators exist, there are also various
optios as to the manner in which a Horizon Situation Indicator displays heading
~nd bearing information and alternatives as to the type of signal that drives the
bearing and course movements.
The manner in which the currently preferred embodiment of the
30 invention eslablishes the configuration of digital signal processing unit 12 for
operation with a particular Horizon Situation Indicator is illustrated in
FIGURE 3. As is indicated at block 40 of EIGURE 3, the first step of the
procedure is to determine the reference for the course output. To facilitate this
determination and all other configuration specifications, CPU 18 of the pre-
35 viously mentioned flight management computer is programmed to display"prompts" on cathode ray tube 27 of control and display unit 26, which requests
that the installer specify a required configuration specification. With respect to
specification of the course output reference, the flight management computer
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displays the message "~ISI COURSF OUTPUT I~ RELATIVE TO: ~ ~ " across the
top of cathode ray tube 27 and displays "1 Nose" and "2 North," directly below
that message. To specify the course reference, the installer depresses the
numeric key of keyboard 25 corresponding to either "north" or "nose" and then
5 depresses an ENTER key. As is indicated by block 42 is FIGURE 3, CPU 18 is
programmed to then display a message on cathode ray tube 27 which requests
that the installer specify whether a resolver or synchro signal is employed in the
system to drive the course indicating movement of the system Horizon Situation
Indicator. When the installer has depressed the appropriate key of keyboard 25
10 and has pressed the ENTER key, the system sequences to the configuration
determination indicated at block 44 of FI5URE 3. At this point, the system
displays a message on cathode ray tube 27 requesting the installer to specify
whether the bearing information displayed on the Horizon Situation Indicator
being used in the system is relative to the aircraft "nose", or is relative to
15 "North". When the appropriate information has been entered in the previously
indicated manner, CPU 18 sequences to the step indicated at block 46, causing
cathode ray tube 27 to display a message requesting that the installer indicate
whether the bearing signal displayed on the Horizon Situation Indicator is offset
by 0 (no offset) or is offset by 180. Following entry of the appropriate
20 configuration specification, CPU 18 causes cathode ray tube 27 to display a
message requesting that the installer enter the type of bearing to be displayed by
the Horizon Situation Indicator. During this step, which is indicated at block 48
of FIGURE 3, the installer specifies whether the bearing that will be displayed
on the Horizon Situation Indicator is relative to: (1) a selected waypoint (e.g., a
25 specified transmitter location of a navigation aid or a particular geographiclocation that is entered by longitude and lattitude); (2) the aircraft ground track;
or, (3) a desired aircraft heading. During the final step of the Horizon Situation
Indicator configuration specification, which is indicated at block 50 of
FIGURE 3, CPU 18 causes cathode ray tube 27 to request entry of the type of
30 signal that will drive the bearing mechanism of the Horizon Situation Indicator
that provides bearing information. When the installer has entered an appropriateresponse (e.g., synchro or resolver), CPU 18 sequences to the next required
configuration determination (indicated at block 52 of FIGURE 3).
As will be recognized by those skllled in the art, configuration
35 specifications for eech alternative signal service and signal utilization device
can be determined in the manner indicated in FIGURE 3 and discussed above. In
some cases, a particular configuration determination will require a series of
steps such as those illustrated in FIGURE 3. In other cases, a single
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specification step will provide the required configuration information. For
example, in the previously mentioned flight management computer that employs
the invention, selection of the true airspeed input signal source is accomplished
by a single inquiry wherein the system installer depresses one of seven indicated
5 keys of keyboard 25 to indicate that either that no true airspeed input is utilized
in that particular configuration, or to indicate which of six optional true airspeed
input signals is to be provided to the system digital processor.
As is indicated by block 54 of FIGVE~E 3, when the installer has
specified all configuration information necessary to irnplement a new installation
10 or to change an existing installation, a binary signal code representative of the
operational configuration of digital signal processing unit 12 is written into
configuration memory 32 of configuration module 30. In the currently preferred
embodiments in the invention, such as the flight management computer tha$ is
discussed herein, CPU 18 of digital signal processing unit 12 causes cathode ray15 tube 2~ to display Q message requesting the installer to depress a first key (e.g.,
"1") if the configuration data is not to be written into configuration memory 32or to depress Q second specified key (e.g., "2") if the data is to be written into
configuration memory 32. When the configuration data is to be written into
configuration module 30, CPU 18 sequences to erase the appropriate memory
20 registers of configuration memory 32 and io supply the configuration data as a
serially formatted signal.
For example, the type NMC 9306/COP 494 programmable non-
volatile memory that is utilized in current realizations of the invention, is
organized to store data in 16 registers, each containing 16 bits. To write the
25 configuration code into one or more registers of this memory, CPU 18 sequences
to supply the memory with operational codes that cause configuration
memory 32 to erase the appropriate memory registers and cause the configura-
tion data (which is stored in the random access memory of CPU 18 during the
steps of the configuration specification) to be sequentially written into the
30 registers of configuration memory 32. Once the configuration data is written
into configuration memory 32, the data is read by digital signal processing
unit 12 each time the avionics system is activated. Thus, when digital signal
processing unit 12 is replaced for normal maintenance or because of suspected
malfunction, proper configuration data is supplied to the newly installed signal35 processing unit 1~ without further action by maintenance personnel.
Although configuration memory 32 of the currently preferred
embodiments of the invention is organized as 16 16-bit registers, it should be
noted that, in the preferred embodiments of the invention, the configuration
~2~3~16
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data is organized as a single binary encoded instruction having a predetermined
format. That is, the configuration data is organized RS nn ordered set of binaryencoded signals wherein the selected configuration of each signal source 14 and
each signal utilization device 16 is specified by 8 group of binary encoded
5 signals. For example, in the implementation of the invention that is utilized in
the previously mentioned flight management computer, the specification of the
Horizontal Situation Indicator configuration data consists of a group of seve
binary bits. To functionally aSSOCiQte the various parameters being specified,
this group of seven binary bits is subdivided into three 2-bit characters and one
10 1-bit character. ln the particular organization employed, the 1-bit character is
the least significant bit of the Horizontal Situation Indicator 7-bit code and
specifies whether the course output is relative to the aircraft nose or North.
The 2-bit character that constitutes the next two least significant bits of the
code specifies whether the Horizontal Situation Indicator bearing signal
15 is: (1) relative to the ~ircraft nose with 180~ offset; (2) relative to North with
180 offset; (3) relative to the aircraft nose with 0 offset; or (4) is relative to
North with 0 offset. The character defined by the two next most signiicant
bits specifies whether the aircraft bearing is relative to: (1) a waypoint; (2) the
aircraft ground track; or (3) a desired heading. The final character (i.e., the two
20 most significant bits of the Horizontal Situtation Indicator code) specifies
whether: (1) a resolver signal is utilized for both course and heading signals;
(2) a synchro signal is utilized for Rircraft course and a resolver signal is utilized
for heading; (3) a resolver signal is utilized for aircraft course and a synchrosignal is utilized for heading; or (4) a synchro signal is utilized for both aircraft
25 heading and course.
It will be recognized by those skilled in the art that organizing the
configuration data in the above-described manner, rather than organizing the
signal into a plurality of data words having equal bit length, reduces the amount
of memory required for storing the configuration data. Further, those skilled in30 the art will recognize that various other data compression techniques can be
employed to further reduce the required amount of memory.
In addition to the above-discussed aspects and features of the
invention, in the currently preferred embodiments, digital signal processing
unit 12 is configured and arranged to periodically verify the configuration data35 stored in configuration memory 32. In this regard, and as pr~viously mentioned!
CPU 18 sequences digital signal processing unit 12 so that the configuration data
is accessed each time that power is applied to the avionics system (i.e., the
system is "powered-up"). In the previously mentioned flight management
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-13-
computer that employs tne invention, CPU 18 includes nonvolatile random access
memory and CPU 18 writes the configuration data into a predetermined portion
of this memory whenever the configuration clata is written into configuration
memory 32 (e.g., initial installation or modification of the system). When the
S configuration data is subsequently accessed during each system power-up
sequence, the data stored in the nonvolatile random access memory of CPU 18 is
compared with the data supplied by configuration memory 32. In addition, in the
currently preferred embodiments of the invention, conventional error detection
(such as check-sum, parity, or Hamming code tests~ is perîormed relative to both10 sets of data. If the two sets of data are identical and no errors are detected by
either set of data, the system power-up sequence continues. On the other hand,
if discrepancies a~e detected, a warning signal is supplied (e.g., to control and
display unit 26 of FIGURE 1). This provides early detection of a malfunction
within either configuration memory 32 or digital signal processing unit 12.
Those skilled in the art will recognize that the embodiments of the
invention discussed herein are exemplary in nature and that vnrious changes and
modifications can be made without departing from the scope and the spirit of the invention. For example, although the invention has been described in terms of Q
digital signal processing unit, it can be recognized that the invention can be
20 practiced with analog signal processors by providing dedicated digital circuitry
for determining an appropriate digitally encoded signal and storing that signal in
configuration memory 32. Further, although the input signal sources discussed
relative to the illustrative embodiment of the invention are conventional sensors
and transducers, the invention is applicable to all types of input signals and
25 information. For example, the invention is well suited for providing input signals
and codes such as the previously mentioned aircraft identification and other
information that may control the operating characteristics of a particular signal
processing unit.
