U.S. patent application number 16/993986 was filed with the patent office on 2022-02-17 for method and apparatus for memory error detection.
The applicant listed for this patent is Rockwell Automation Technologies, Inc.. Invention is credited to Jonathan R. Engdahl, Anthony G. Gibart, Joseph P. Izzo, Benjamin H. Nave.
Application Number | 20220050740 16/993986 |
Document ID | / |
Family ID | |
Filed Date | 2022-02-17 |
United States Patent
Application |
20220050740 |
Kind Code |
A1 |
Gibart; Anthony G. ; et
al. |
February 17, 2022 |
Method and Apparatus for Memory Error Detection
Abstract
A system with multiple processing domains sharing a memory
resource accessed via a shared memory controller detects a memory
error. As data is written to the shared memory resource, each
processing domain generates a diagnostic code as a function of the
data, the memory address for the data, and of a unique identifier
corresponding to the processing domain. The diagnostic code is
stored with the data for verification when the data is read back.
As the data is read back, the processing domain separates the
diagnostic code from the data being read and generates another
diagnostic code in the same manner as the original diagnostic code.
The other diagnostic code is compared to the initial diagnostic
code. If both diagnostic codes are the same, the processing domain
can be confident that the data read from the shared memory resource
is the same as the data that was originally written.
Inventors: |
Gibart; Anthony G.; (New
Berlin, WI) ; Izzo; Joseph P.; (New Berlin, WI)
; Engdahl; Jonathan R.; (Chardon, OH) ; Nave;
Benjamin H.; (Shaker Height, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Rockwell Automation Technologies, Inc. |
Mayfield Heights |
OH |
US |
|
|
Appl. No.: |
16/993986 |
Filed: |
August 14, 2020 |
International
Class: |
G06F 11/10 20060101
G06F011/10 |
Claims
1. A method for detecting a memory error, the method comprising the
steps of: writing first data to a first memory address in a shared
memory resource from a first processing domain; generating a first
diagnostic code with the first processing domain as a function of
the first data and of the first memory address; appending the first
diagnostic code to the first data such that the first diagnostic
code is written in the shared memory resource with the first data;
reading the first data and the first diagnostic code from the
shared memory resource back to the first processing domain;
verifying that the first data read from the shared memory resource
matches the first data written to the shared memory resource with
the first processing domain; writing second data to a second memory
address in the shared memory resource from a second processing
domain; generating a second diagnostic code with the second
processing domain as a function of the second data and of the
second memory address; appending the second diagnostic code to the
second data such that the second diagnostic code is written in the
shared memory resource with the second data; reading the second
data and the second diagnostic code from the shared memory resource
back to the second processing domain; and verifying that the second
data read from the shared memory resource matches the second data
written to the shared memory resource with the second processing
domain.
2. The method of claim 1 wherein the first diagnostic code is a
checksum generated by passing the first data and the first memory
address through a corresponding checksum algorithm.
3. The method of claim 1 wherein verifying that the first data read
from the shared memory resource matches the first data written to
the shared memory resource further comprises the steps of:
generating an additional first diagnostic code with the first
processing domain as a function of the first data and the first
memory address with the first processing domain as the first data
is read from the shared memory resource; comparing the first
diagnostic code read from the shared memory resource to the
additional first diagnostic code with the first processing domain;
and verifying that the first data read from the shared memory
resource matches the first data written to the shared memory
resource when the first diagnostic code read from the shared memory
resource matches the additional first diagnostic code.
4. The method of claim 3 wherein the first processing domain
generates a memory error when the first diagnostic code read from
the shared memory resource does not match the additional first
diagnostic code.
5. (canceled)
6. The method of claim 1 wherein the first processing domain and
the second processing domain both use a single memory controller
for writing the first data and the second data, respectively, to
the shared memory resource.
7. The method of claim 1 wherein the first processing domain
includes a first unique identifier when generating the first
diagnostic code and the second processing domain includes a second
unique identifier when generating the second diagnostic code.
8. The method of claim 7 wherein: the step of verifying that the
first data read from the shared memory resource matches the first
data written to the shared memory resource with the first
processing domain further comprises using the first unique
identifier to verify the first data was written by the first
processing domain, and the step of verifying that the second data
read from the shared memory resource matches the second data
written to the shared memory resource with the second processing
domain further comprises using the second unique identifier to
verify the second data was written by the second processing
domain.
9. The method of claim 1 wherein verifying that the first data read
from the shared memory resource matches the first data written to
the shared memory resource further comprises the steps of:
generating another first diagnostic code with the first processing
domain as a function of the first data and the first memory address
with the first processing domain as the first data is read from the
shared memory resource, comparing the first diagnostic code read
from the shared memory resource to the other first diagnostic code
with the first processing domain, and verifying that the first data
read from the shared memory resource matches the first data written
to the shared memory resource when the first diagnostic code read
from the shared memory resource matches the other first diagnostic
code; and wherein verifying that the second data read from the
shared memory resource matches the second data written to the
shared memory resource further comprises the steps of: generating
another second diagnostic code with the second processing domain as
a function of the second data and the second memory address with
the second processing domain as the second data is read from the
shared memory resource, comparing the second diagnostic code read
from the shared memory resource to the other second diagnostic code
with the second processing domain, and verifying that the second
data read from the shared memory resource matches the second data
written to the shared memory resource when the second diagnostic
code read from the shared memory resource matches the other second
diagnostic code.
10. The method of claim 9 wherein: the first processing domain
generates a first memory error when the first diagnostic code read
from the shared memory resource does not match the other first
diagnostic code, and the second processing domain generates a
second memory error when the second diagnostic code read from the
shared memory resource does not match the other second diagnostic
code.
11. The method of claim 10 wherein: the first processing domain is
in communication with the second processing domain, the first
processing domain notifies the second processing domain of the
first memory error, and the second processing domain notifies the
first processing domain of the second memory error.
12. An apparatus for detecting a memory error, comprising: a shared
memory resource configured to store first data and second data; a
memory controller configured to: manage reading the first data and
the second data from the shared memory resource, and manage writing
the first data and the second data to the shared memory resource; a
first processing domain in communication with the memory
controller, wherein the first processing domain is configured to:
write the first data to the shared memory resource via the memory
controller, generate a first diagnostic code corresponding to the
first processing domain, the first data to be written, and to a
memory address at which the first data is to be written, and append
the first diagnostic code to the first data as it is written to the
shared memory resource; and a second processing domain in
communication with the memory controller, wherein the second
processing domain is configured to: write the second data to the
shared memory resource via the memory controller, generate a second
diagnostic code corresponding to the second processing domain, the
second data to be written, and to a memory address at which the
second data is to be written, and append the second diagnostic code
to the second data as it is written to the shared memory resource,
wherein either the first or the second processing domain is further
configured to: read the first or second data from the shared memory
resource via the memory controller, and verify that the first or
second data read from the shared memory resource matches the first
or second data written to the shared memory resource.
13. The apparatus of claim 12 wherein the first processing domain
includes a first unique identifier when generating the first
diagnostic code and the second processing domain includes a second
unique identifier when generating the second diagnostic code.
14. The apparatus of claim 13 wherein: the first processing domain
is further configured to verify that the first data read from the
shared memory resource matches the first data written to the shared
memory resource using the first unique identifier; and the second
processing domain is further configured to verify that the second
data read from the shared memory resource matches the second data
written to the shared memory resource using the second unique
identifier.
15. The apparatus of claim 14 wherein: the first processing domain
is configured to verify that the first data read from the shared
memory resource by the first processing domain matches the first
data written to the shared memory resource by the first processing
domain by: generating another first diagnostic code with the first
processing domain as a function of the first data read, the memory
address from which the first data was read, and the first unique
identifier as the first data is read from the shared memory
resource, and verifying that the first data read from the shared
memory resource by the first processing domain matches the first
data written to the shared memory resource by the first processing
domain when the first diagnostic code read from the shared memory
resource matches the other first diagnostic code; and the second
processing domain is configured to verify that the second data read
from the shared memory resource by the second processing domain
matches the second data written to the shared memory resource by
the second processing domain by: generating another second
diagnostic code with the second processing domain as a function of
the second data read, the memory address from which the second data
was read, and the second unique identifier as the second data is
read from the shared memory resource, and verifying that the second
data read from the shared memory resource by the second processing
domain matches the second data written to the shared memory
resource by the second processing domain when the second diagnostic
code read from the shared memory resource matches the other second
diagnostic code.
16. The apparatus of claim 15 wherein: the first processing domain
generates a first memory error when the first diagnostic code read
from the shared memory resource does not match the other first
diagnostic code, and the second processing domain generates a
second memory error when the second diagnostic code read from the
shared memory resource does not match the other second diagnostic
code.
17. The apparatus of claim 16 wherein: the first processing domain
is in communication with the second processing domain, the first
processing domain notifies the second processing domain of the
first memory error, and the second processing domain notifies the
first processing domain of the second memory error.
18. A method for detecting a memory error, the method comprising
the steps of: writing data to a memory address in a shared memory
resource via a shared memory controller from either a first
processing domain or a second processing domain; appending a
diagnostic code to the data as the data is written by either the
first processing domain or the second processing domain, wherein
the diagnostic code is generated as a function of the data, the
memory address, and either the first or second processing domain
from which it is written; reading the data from the memory address
in the shared memory resource with the corresponding processing
domain that wrote the data to the memory address; and verifying
that the data read from the memory address in the shared memory
resource matches the data written to the memory address using the
diagnostic code appended to the data.
19. The method of claim 18 wherein: the first processing domain
includes a first unique identifier; the first processing domain
generates the diagnostic code as a further function of the first
unique identifier; the second processing domain includes a second
unique identifier; and the second processing domain generates the
diagnostic code as a further function of the second unique
identifier.
20. The method of claim 19 wherein: the first processing domain
verifies that the data read from the memory address in the shared
memory resource matches the data written to the memory by:
generating a first additional diagnostic code as a function of the
data read, the memory address from which the data is read, and of
the first unique identifier, and verifying that the data read from
the memory address in the shared memory resource matches the data
written to the memory when the first additional diagnostic code
matches the diagnostic code which was stored in the shared memory
resource; and the second processing domain verifies that the data
read from the memory address in the shared memory resource matches
the data written to the memory by: generating a second additional
diagnostic code as a function of the data read, the memory address
from which the data is read, and of the second unique identifier,
and verifying that the data read from the memory address in the
shared memory resource matches the data written to the memory when
the second additional diagnostic code matches the diagnostic code
which was stored in the shared memory resource.
Description
BACKGROUND INFORMATION
[0001] The subject matter disclosed herein relates to detecting a
memory error in a system with multiple processing domains, and,
more specifically, to an industrial controller configured to meet
safety integrity level three (SIL-3) functional safety with a
single processor chip.
[0002] Industrial controllers are special-purpose computers used in
controlling industrial processes. Under the direction of a stored
control program, an industrial controller examines a series of
inputs reflecting the status of the controlled process and changes
a series of outputs controlling the process. The inputs and outputs
may be binary, that is, on or off, or analog, providing a value
within a substantially continuous range. The inputs may be obtained
from sensors attached to the controlled process, and the outputs
may be signals to actuators on the controlled process.
[0003] "Safety industrial control systems" are industrial control
systems intended to ensure the safety of humans working in the
environment of an industrial process. Such systems may include the
electronics associated with emergency-stop buttons, light curtains,
and other machine lockouts. Safety industrial control systems are
not optimized for "availability", that is being able to function
for long periods of time without error, but rather for "safety"
which is being able to accurately detect an operating condition
requiring a shut down. Safety industrial controllers normally
provide a predetermined safe state for their outputs upon a safety
shutdown, the predetermined values of these outputs being intended
to put the industrial process into its safest static mode.
[0004] Safety industrial control systems may be associated with a
"safety integrity level" (SIL) indicating a given amount of risk
reduction. Standard IEC EN 61508 defines four SIL levels of SIL-1
to SIL-4 with higher numbers representing higher amounts of risk
reduction. To achieve SIL-3 functional safety, high diagnostic
coverage of critical components is required such that a failure of
a critical component does not go undetected.
[0005] A common method for providing the required diagnostic
coverage is to provide redundant components. Each component is
configured to generate an identical signal, execute identical
processing steps, or the like. While one of the components may be
selected as an active component and may be configured to interface
with the controlled machine or process, both the active component
and a backup component operate in tandem and operation of the
components may be compared to each other. A comparison of signals
generated or processing steps executed should return identical
results if both components are operating normally. A difference
between the operation of the two components indicates failure of
one of the components and the system may take the necessary steps
to enter a safe operating state.
[0006] The redundancy involved with providing safety systems is
relatively expensive and accordingly there is considerable interest
in lowering the price point of such systems such as could increase
their relative availability and thus overall safety of the
community. One significant source of cost is the need for multiple
microprocessors. Recent processor architectures used in industrial
controllers have moved to "multicore" architectures in which
multiple processing cores are contained inexpensively on a single
integrated circuit die.
[0007] The use of multiple processing cores on a single chip does
not, however, eliminate all redundancy associated with multiple
microprocessors. Accompanying multiple microprocessors are
similarly redundant memory devices as well as memory controllers
interconnected between the microprocessor and the memory device. In
order to maintain redundancy, each processing core on a single
integrated circuit die would still require a separate memory
controller and separate memory. The memory controller is a power
intensive device and the redundant memory devices require more
physical space on a circuit board than a single memory device
having similar storage capacity.
[0008] Thus, it would be desirable to provide an improved system
for managing memory usage for multiple processing domains.
BRIEF DESCRIPTION
[0009] According to one embodiment of the invention, a method for
detecting a memory error includes writing data to a memory address
in a shared memory resource from a first processing domain,
generating a diagnostic code with the first processing domain as a
function of the data and of the memory address, and appending the
diagnostic code to the data such that the diagnostic code is
written in the shared memory resource with the corresponding data.
The data and the diagnostic code are read from the shared memory
resource back to the first processing domain, and the first
processing domain verifies that the data read from the shared
memory resource matches the data written to the shared memory
resource.
[0010] According to another embodiment of the invention, an
apparatus for detecting a memory error includes a shared memory
resource configured to store data, a memory controller, a first
processing domain, and a second processing domain. The memory
controller is configured to manage reading the data from and
writing the data to the shared memory resource. The first
processing domain is in communication with the memory controller
and is configured to write the data to the shared memory resource
via the memory controller, generate a first diagnostic code
corresponding to the first processing domain, the data to be
written, and to a memory address at which the data is to be
written, and append the first diagnostic code to the data as it is
written to the shared memory resource. The second processing domain
is in communication with the memory controller and is configured to
write the data to the shared memory resource via the memory
controller, generate a second diagnostic code corresponding to the
second processing domain, the data to be written, and to a memory
address at which the data is to be written, and append the second
diagnostic code to the data as it is written to the shared memory
resource. Either the first or the second processing domain is
further configured to read the data from the shared memory resource
via the memory controller, and verify that the data read from the
shared memory resource matches the data written to the shared
memory resource.
[0011] According to still another embodiment of the invention, a
method for detecting a memory error writes data to a memory address
in a shared memory resource via a shared memory controller from
either a first processing domain or a second processing domain and
appends a diagnostic code to the data as the data is written by
either the first processing domain or the second processing domain.
The diagnostic code is generated as a function of the data, the
memory address, and the corresponding processing domain from which
it is written. The data is read from the memory address in the
shared memory resource with the corresponding processing domain
that wrote the data to the memory address, and the data read from
the memory address in the shared memory resource is verified that
it matches the data written to the memory address using the
diagnostic code appended to the data.
[0012] These and other advantages and features of the invention
will become apparent to those skilled in the art from the detailed
description and the accompanying drawings. It should be understood,
however, that the detailed description and accompanying drawings,
while indicating preferred embodiments of the present invention,
are given by way of illustration and not of limitation. Many
changes and modifications may be made within the scope of the
present invention without departing from the spirit thereof, and
the invention includes all such modifications.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Various exemplary embodiments of the subject matter
disclosed herein are illustrated in the accompanying drawings in
which like reference numerals represent like parts throughout, and
in which:
[0014] FIG. 1 is a block diagram representation of an exemplary
multicore processor incorporating one embodiment of the present
invention;
[0015] FIG. 2 is a block diagram representation of data being
written by one core of the processor illustrated in FIG. 1;
[0016] FIG. 3 is a flow diagram illustrating the steps for writing
data to a shared memory resource by one of the cores in the
processor of FIG. 1 according to one embodiment of the invention;
and
[0017] FIG. 4 is a flow diagram illustrating the steps for reading
data from a shared memory resource by one of the cores in the
processor of FIG. 1 according to one embodiment of the
invention.
[0018] In describing the various embodiments of the invention which
are illustrated in the drawings, specific terminology will be
resorted to for the sake of clarity. However, it is not intended
that the invention be limited to the specific terms so selected and
it is understood that each specific term includes all technical
equivalents which operate in a similar manner to accomplish a
similar purpose. For example, the word "connected," "attached," or
terms similar thereto are often used. They are not limited to
direct connection but include connection through other elements
where such connection is recognized as being equivalent by those
skilled in the art.
DETAILED DESCRIPTION
[0019] The various features and advantageous details of the subject
matter disclosed herein are explained more fully with reference to
the non-limiting embodiments described in detail in the following
description.
[0020] The subject matter disclosed herein discloses an improved
system for managing memory usage for multiple processing domains.
More specifically, an improved method and apparatus is described
for detecting a memory error in a system with multiple processing
domains on a single integrated circuit die, where each of the
processing domains utilizes a shared memory resource accessed via a
shared memory controller. Each processing domain issues read and
write commands to the shared memory controller for storing data in
and reading data from the shared memory resource. As data is
written to the shared memory resource, the processing domain
generates a diagnostic code that may be used when reading the data
back from the shared memory resource to verify that the data read
is the same as the data that was written.
[0021] The diagnostic code is generated as a function of the data
being written, the memory address to which the data is being
written, and of a unique identifier corresponding to the processing
domain which is writing the data. According to one embodiment of
the invention, a checksum, such as a cyclic redundancy check (CRC),
may be performed on the data and on the address within the shared
memory resource to which the data is to be written. A CRC checksum
is generated by an algorithm which receives data to be stored as an
input and passes the data through a function, such as a polynomial
function which outputs a unique signature based on the data
received and on the function generating the signature. By including
the address at which the data is to be written, the signature will
be different than a signature generated solely based on the data.
By further incorporating a unique identifier corresponding to the
processing domain, identical data written to the same address by
each processing domain would still generate a unique checksum for
each processing domain. Optionally, it is contemplated that each
processing domain may utilize a unique polynomial or other
processing algorithm by which the checksum is generated. In either
event, the resulting diagnostic code is a function of the
processing domain which generated the code. The diagnostic code is
stored with the data in the shared memory for verification when the
data is read back from the shared memory resource.
[0022] When the data is read back from the shared memory resource,
the processing domain separates the diagnostic code and the data
being read. The processing domain generates another diagnostic code
as a function of the data being read, the memory address from which
the data is being read, and of the unique identifier corresponding
to the processing domain which is reading the data. Inclusion of
the memory address in generation of the diagnostic code allows the
processing domain to check, for example, whether another set of
data was erroneously written by the memory controller to that
address. Because the diagnostic code includes the memory address,
data that should have been written to a different address will
include a diagnostic code that was generated as a function of the
different address. Even if identical data intended for a different
memory location is written to a particular address, the diagnostic
code will correspond to the different memory address and the error
made by the memory controller in writing data to an incorrect
memory location will be detected when reading the data. Similarly,
including a unique identifier and/or using a unique algorithm by
which the diagnostic code is generated within each processing
domain ensures that only the domain that wrote the data to the
shared memory resource will be able to read the data from the
memory resource. The other diagnostic code is generated in an
identical manner to the initial diagnostic code as the data is read
from the shared memory resource. The other diagnostic code is then
compared to the initial diagnostic code. If both diagnostic codes
are the same, the processing domain can be confident that the data
read from the shared memory resource is the same as the data that
was originally written.
[0023] Turning initially to FIG. 1, an exemplary multicore
microprocessor 10 incorporating one embodiment of the present
invention is illustrated. According to the illustrated embodiment,
the microprocessor 10 includes a first processing domain 100 and a
second processing domain 200. The first processing domain 100
includes a first processor core 105, and the second processing
domain 200 includes a second processor core 205. Although, the
microprocessor 10 is shown with two cores 105, 205 and two
processing domains 100, 200, this is for ease of illustration and
is not intended to be limiting. It is contemplated that the
microprocessor 10 may include more than two cores and processing
domains. Each processing domain 100, 200 further includes a local
cache memory 110, 210. The first processor core 105 can read from
and write to the first cache 110, and the second processor core 205
can read from and write to the second cache 210.
[0024] Each processing domain 100, 200 is also in communication
with a shared memory resource 30 via a common memory controller 20.
Although illustrated as a single block, it is contemplated that the
shared memory resource 30 may be a single memory chip or multiple
memory chips each in communication with the memory controller 20.
The first processing domain 100 includes a first write channel 115
receiving data from the first processing core 105. The first write
channel 115 is in communication with a first diagnostic circuit 120
to generate a diagnostic code corresponding to data being written
to the shared memory resource 30. The first processing domain 100
also includes a first read channel 125 receiving data from the
memory controller 20. The first read channel 125 is also in
communication with the first diagnostic circuit 120 to generate a
diagnostic code corresponding to data being read from the shared
memory resource 30. A first compare circuit 130 is in communication
with both the first read channel 125 and the first diagnostic
circuit 120 to compare the diagnostic code generated when writing
the data to the diagnostic code generated when reading the data.
The second processing domain 200 includes a second write channel
215 receiving data from the second processing core 205. The second
write channel 215 is in communication with a second diagnostic
circuit 220 to generate a diagnostic code corresponding to data
being written to the shared memory resource 30. The second
processing domain 200 also includes a second read channel 225
receiving data from the memory controller 20. The second read
channel 225 is also in communication with the second diagnostic
circuit 220 to generate a diagnostic code corresponding to data
being read from the shared memory resource 30. A second compare
circuit 230 is in communication with both the second read channel
225 and the second diagnostic circuit 220 to compare the diagnostic
code generated when writing the data to the diagnostic code
generated when reading the data.
[0025] Although illustrated as separate circuits within the
respective processing domains, it is contemplated that circuits may
be combined in whole or in part with other circuits. For example,
the diagnostic circuit 120, 220 and the compare circuit 130, 230
may be formed as a single circuit. The separate circuits are
utilized for ease of illustration and for ease of discussion of
various functions performed during a read or write between the
processor 10 and the shared memory resource 30. Similarly, each
channel 115, 125, 215, 225 is illustrated as a separate
communication channel. The separate channels are illustrated for
ease of illustration and discussion of the communication along each
channel. It is contemplated that a single communication bus may be
provided for each processing domain 100, 200 where a single
processing bus includes both the respective read and write channel
for the corresponding processing domain. It is further contemplated
that a single communication bus may be provided between the
processor 10 and the memory controller 20 and that a suitable bus
interface is included on the processor 10 to route communication
between each processing domain and the memory controller. According
to still another embodiment of the invention, it is contemplated
that each processor core 105, 205 may be implemented on a separate
processor rather than as a multi-core processor, where each of the
separate processors writes to the shared memory controller 20 and
shared memory 30.
[0026] In operation, each processing domain 100, 200 is able to
detect memory errors related to data written to the shared memory
resource 30 by the respective processing domain. For convenience,
the process will be discussed with respect to the first processing
domain 100. This is not intended to be limiting and it is
understood that the second processing domain 200 or still
additional processing domains may be configured to execute the same
steps to detect a memory error for data written to the shared
memory resource 30 by the corresponding processing domain.
[0027] Turning next to FIG. 3, steps for writing data to the shared
memory resource 30 are illustrated. At step 302, the data and
address are prepared by the processing core 105 for writing to the
shared memory resource 30. With reference also to FIG. 2, an
exemplary data packet 50 is illustrated which includes a header 52,
data 54 to be written, and a diagnostic code 56. The address 53 at
which the data 54 is to be written is included in the header
information. This data packet 50 is intended to be exemplary only
and not limiting. It is contemplated that the header 52 may include
only an address 53 at which the data 54 is to be written.
Optionally, the header may also include, for example, a source,
indicating to the memory controller 20 from which processing domain
100 the data is being sent, or other control commands and or status
flags to manage the read and write process between each processing
domain 100 and the shared memory resource. According to still
another embodiment of the invention, an address bus, separate from
a data bus, may be provided between each processing domain 100 and
the memory controller 20, where the address 53 at which the data 54
is to be written within the shared memory resource 30 is provided
on the address bus by the processor core 105 and the data 54 is
provided on the data bus by the processor core 105.
[0028] With reference again to FIG. 3, the processing domain 100
next generates a diagnostic code 56 for the data to be written to
the shared memory resource 30, as shown in step 304. The diagnostic
circuit 120 receives the data 54 and address 53 at which the data
is to be written. These may be provided in a single data packet 50
or via separate buses within the processing domain 100. The
diagnostic circuit 120 is then configured to generate a diagnostic
code as a function of the data 54 and of the address 53 at which
the data is to be written. It is contemplated that the data 54 may
include, for example, between sixteen and one hundred twenty-eight
(16-128) bits. The address may similarly be defined by a sixteen to
one hundred twenty-eight (16-128) bit memory location. The length
of the data 54 and the length of the address 53 are defined by the
shared memory resource 30 and/or the memory controller 20 used to
transfer the data 54 between the processing domain 100 and the
shared memory resource. The data 54 and address 53 are provided to
the diagnostic circuit and passed through a suitable algorithm to
generate the diagnostic code 56. The diagnostic code may be
generated via a hash algorithm, where the hash algorithm is
configured to map a set of data values to a set of code values with
a high probability that a change in the data values will result in
a change in the code generated. As previously indicated, the
diagnostic code 56 may be a CRC checksum, and the algorithm may be
any suitable algorithm to generate the CRC checksum. According to
still other embodiments, the diagnostic code 56 may be generated by
an Error Correcting Code (ECC) or a Secure Hash Algorithm
(SHA).
[0029] It is further contemplated that a unique identifier for each
processing domain 100 may be included with the data 54 and the
address 53 to further identify the data 54 as having been written
to the shared memory resource 30 by a particular processing domain
100. According to one embodiment of the invention, one bit of the
address 53 or of the data 54 to be stored to the shared memory
resource 30 may be used to define the unique identifier. If there
are only two processing domains, as illustrated in FIG. 1, the
highest address bit may be used to define a particular processing
domain. The first processing domain 100 may be assigned zero (0) as
an identifier, and the second processing domain 200 may be assigned
one (1) as an identifier. If, for example, a thirty-two (32) bit
address 53 is utilized, the processing core 105 may write an
address to the lower thirty-one (31) bits. The upper bit may be
tied to a logical zero for the first processing domain 100 and to a
logical one for the second processing domain 200 such that the
address is always defined as a function of the processing domain.
Optionally, each processing core 105 may be configured to set the
upper bit to the respective identifier as it writes the remaining
bits of the address. Similarly, two bits may be reserved for unique
identifiers if there are four processing domains and so on for a
greater number of processing domains. According to still another
option, a separate data byte may be defined in which up to two
hundred fifty-five unique codes may be defined for separate
processing domains. According to yet another option, the source of
the data 54, defining one of the processing domains 100, may be
included in the header 52 and may serve as the unique identifier.
The separate data byte may be passed to the algorithm generating
the diagnostic code in tandem with the data 54 and the address 53,
such that the CRC is determined as a function of the unique
identifier, the data, and the address at which the data is to be
written.
[0030] According to yet another aspect of the invention, the unique
identifier may be a unique algorithm selected for each processing
domain 100. When each processing domain 100 passes the data 54 and
address 53 to the algorithm, a different diagnostic code 56, or
checksum, would be generated for the processing domain according to
the selected algorithm. As a result, identical data being written
to the same address would still generate a different diagnostic
code 56 for each processing domain 100. Thus, the processing domain
100 could verify that data read back from the shared memory
resource 30 was, in fact, written by that processing domain, as
will be discussed in more detail below.
[0031] Referring again to FIG. 3, the diagnostic code 56 is written
to the shared memory resource 30 along with the data 54 at the
desired address 53, as shown in step 306. According to one
embodiment of the invention, the diagnostic circuit 120 appends the
diagnostic code 56 to the data 54 and transmits both the data 54
and the diagnostic code 56 to the memory controller 20 via a data
bus. The address 53 may be passed to the memory controller 20
either directly from the processing core 105 or via the diagnostic
circuit 120 on an address bus. Optionally, the address 53 is passed
first to the diagnostic circuit 120, for example, in a header 52,
and the data packet 50 is passed as a single object from the
diagnostic circuit 120 to the memory controller 20. Once the memory
controller 20 has received the address 53, data 54, and diagnostic
code 56, the memory controller 20 manages storing the data 54 and
the diagnostic code 56 in the shared memory resource 30.
[0032] Turning next to FIG. 4, steps for reading data from the
shared memory resource 30 are illustrated. At step 402, the
processing domain 100 issues a read request to the memory
controller 20. The read request identifies a memory address 53 from
which the processing domain 100 wishes to read data 54. The memory
controller 20 manages the data access with the shared memory
resource 30 and provides the requested data 54 from the shared
memory resource 30. When the memory controller 20 reads the data
54, the diagnostic code 56 corresponding to the data 54 is also
read. The data 54 and diagnostic code 56 are stored in consecutive
bytes of memory and, therefore, a read of the shared memory
resource 30 defines the desired address 53 and requests a length of
data to be read that is sufficient to return both the data 54 and
the diagnostic code 56 which was previously stored with the data
54.
[0033] During the read process, the processing domain 100 performs
a check on the data read back from the shared memory resource 30 to
verify that it corresponds to the data originally written. When the
data 54 and diagnostic code 56 are transferred from the shared
memory resource 30 to the processing domain 100 by the memory
controller 20, the read channel 125 is configured to split the data
54 and the diagnostic code 56 from each other for separate
processing. The read channel 125 may, for example, connect the
portion of the data bus on which the data 54 is transmitted to the
diagnostic circuit 120 and the portion of the data bus on which the
diagnostic code 56 is transmitted to a compare circuit 130. As
shown in step 404, another diagnostic code is generated during the
read process. The diagnostic circuit 120 utilizes the same
algorithm used during the write process to generate the new
diagnostic code. The diagnostic circuit 120 receives the data 54
read from the shared memory resource 30 by the memory controller
20. The diagnostic circuit 120 may also receive the desired memory
address 53 from which the data 54 was read directly from the
processing core 105. The same address may be passed both to the
diagnostic circuit 120 and to the memory controller 20 during the
read request to avoid potential errors in the address being
introduced while reading the data. The diagnostic circuit 120 is
also aware of the unique identifier corresponding to the processing
domain 100. Whether the unique identifier is part of the memory
address, a separate bit or byte embedded within the data, or a
unique algorithm used to generate the diagnostic code, the
diagnostic circuit 120 utilizes the unique identifier to generate
the diagnostic code in an identical manner during the read process
as it does during the write process. As a result, the two
diagnostic codes should be identical.
[0034] After generating the second diagnostic code during the read
process, the diagnostic circuit 120 passes the second diagnostic
code to the compare circuit 130. As shown in step 406, the compare
circuit 130 is configured to determine whether the original
diagnostic code, obtained from the shared memory resource 30 is the
same as the new diagnostic code generated during the read process.
If the two diagnostic codes match, the data 54 which was read from
the shared memory resource 30 is verified as matching the data
which was originally written and, as shown in step 408, the data is
then passed to the processing core 105 for subsequent use by the
application or control program which originally initiated the read
request. If, however, the two diagnostic codes do not match, the
compare circuit 130 generates an error, as shown in step 410 and
the processor core 105 takes action based on receiving an error
message rather than upon receiving the requested data.
[0035] If the two diagnostic codes do not match, this could be an
indication of an error occurring at a number of different steps
between the microprocessor 10 and the shared memory resource 30.
For example, an error may occur in the data being written to or
read from the shared memory resource. If the data does not match
between a write and a read, different diagnostic codes will be
generated. Because two processing domains 100, 200 are sharing a
single memory controller, the potential exists for an error in an
address line during a write resulting in one processing domain 100
overwriting a memory address reserved for the other processing
domain 200. However, when the second processing domain 200 attempts
to read data from that address, the diagnostic code which was saved
with the data was generated as a function of a different address.
Thus, when the data is read back, the second processing domain 200
generates a different diagnostic code, using the address at which
the first processing domain erroneously wrote to rather than the
address at which the data was intended to be stored. Thus, the
second processing domain is aware that the data stored in that
memory location is not the same data as was previously written to
that address by the second processing domain.
[0036] If one processing domain 100 detects that an error occurred
in reading data from the shared memory resource 30, the processing
domain 100 that detected the error may notify the other processing
domain 200 of the error. It is contemplated that a separate
communication bus or dedicated signal lines may exist between the
two processing domains 100, 200 by which such an error notification
may be transmitted.
[0037] It should be understood that the invention is not limited in
its application to the details of construction and arrangements of
the components set forth herein. The invention is capable of other
embodiments and of being practiced or carried out in various ways.
Variations and modifications of the foregoing are within the scope
of the present invention. It also being understood that the
invention disclosed and defined herein extends to all alternative
combinations of two or more of the individual features mentioned or
evident from the text and/or drawings. All of these different
combinations constitute various alternative aspects of the present
invention. The embodiments described herein explain the best modes
known for practicing the invention and will enable others skilled
in the art to utilize the invention.
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