Note: Descriptions are shown in the official language in which they were submitted.
CA 02361796 2001-11-09
HARDENED VOYAGE DATA RECORDER
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to apparatus for
recording data regarding the operation of a sea borne
vessel. More particularly, the invention relates to
apparatus for recording and protecting data leading up to
an accident or "incident".
2. Brief Description of the Prior Art
It has long been noted that the investigation
of maritime accidents and incidents could benefit from
the recording of data and audible commands occurring
2~ aboard ships. Indeed, many considered this an inevitable
technological extension of the time-honored ship's
logbook. This desire has culminated in the development
of an international stand:3rd governing the performance of
a Voyage Data Recorder (VI>R) .
CA 02361796 2001-11-09
In 1974 the Safety of Life at Sea (SOLAS)
Convention of the International Maritime Organization
(IMO) acknowledged the value and expressed the desire of
having recorders on ships similar to the "black box"
flight recorders for aircraft. This began a long process
of establishing international standards and requirements
for a Voyage Data Recorder (VDR).
In 1996, VDR requirements, which had been
debated for a long time, began to emerge in the
navigation and electronics subgroup (NAV) of the IMO.
Anticipating an eventual IMO resolution concerning VDRs,
IEC (International Electrotechnical Commission) TC80
formed WG11, which began structuring a specification
based on preliminary drafts of the NAV requirements. The
IMO passed resolution A.861 (20) in November 1997 and the
IEC standard 61996 was completed as a Committee Draft for
Voting in March 1999. The specification was published in
August 2000.
The IEC 61996 Ship borne Voyage Data Recorder
Performance Requirements describes data acquisition and
storage functions and refers to a "protective capsule"
and a "final storage medium". Architecture for complying
with this standard has emerged with two major components.
CA 02361796 2001-11-09
In the first component, the ship's interfaces,
data acquisition, and soft recording functions are
encompassed in a Data Management Unit (DMU). The DMU is
S intended for installation in the relatively benign
environment of the bridge. The second component is the
Hardened Voyage Recorder (HVR) which encompasses the
protective capsule and final storage medium. The HVR is
designed for survivability and recoverability. It is
intended for external installation on the bridge deck or
on top of the superstructure.
The primary function of the Hardened Voyage
Recorder (HVR) is to protect the data acquired by the
Voyage Data Recorder (VDR) so that the data can be used
during accident or "incident" investigation.
SUMMARY OF THE INVENTION
25
It is therefore an object of the invention to
provide a Hardened Voyage Recorder which meets or exceeds
the requirements of the IEC 61996 test specifications,
for the protective capsule and final storage medium.
It is also an object of the invention to
provide a Hardened Voyage Recorder which has a
substantial storage capacity.
CA 02361796 2001-11-09
It is another object of the invention to
provide a Hardened Voyage Recorder which is capable of
recording radar data, audio, and other sensor data.
It is yet another object of the invention to
provide a Hardened Voyage Recorder which has a long life
and low operating power.
It is another object of the invention to
provide a Hardened Voyage Recorder which is easy to
install and service.
It is still another object of the invention to
provide a Hardened Voyage Recorder which easily
interfaces with one or more DMUs.
In accord with these objects which will be
discussed in detail below, the Hardened Voyage Recorder
(HVR) according to the invention includes two separable
subassemblies.
The first subassembly is a mounting base
subassembly designed to be directly fastened to the ship
and provide a watertight cable entry for power and data
connections.
4
CA 02361796 2001-11-09
The second subassembly is a removable hardened
memory subassembly which is attached to the mounting base
with a quick releasing clamp. The hardened memory
subassembly has a bracket for an externally mounted
underwater location beacon with dual activation moisture
sensors to avoid inadvertent activation due to spray,
rain, or hosing off. The HVR is preferably painted a
highly visible florescent orange with white reflective
labels. The reflective labels contain the required text:
VOYAGE DATA RECORDER, DO NOT OPEN, REPORT TO AUTHORITIES.
The mounting base subassembly includes
electronics for receiving data and writing data to the
memory in the hardened memory subassembly.
According to the presently preferred
embodiment, the power connection accepts either 110/220
VAC or 24 VDC and the data connection is an ETHERNET
connection. The AC and DC power connections may both be
active at the same time. The AC connection is preferably
used during normal conditions and the DC connection is
preferably coupled to the ship's UPS (uninterrupted power
supply) .
Further, according to the presently preferred
embodiment, the HVR receives data via TCP/IP (terminal
connection protocol/internet protocol) over ETHERNET.
The HVR is therefore assigned an IP address and is
5
CA 02361796 2004-O1-22
configurable via a "web browser". This also enables the
formation of a network of multiple HVRs all coupled to
numerous sensors via the ETHERNET network.
The removable hardened memory subassembly
preferably includes 1.5 gigabytes of solid state memory
which is protected in a "boiler" such as that disclosed
in co-owned, co-pending Canadian Patent Application No.
2,361,797, filed November 9, 2001.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an HVR
according to the invention;
FIG. 2 is a side elevation view of an HVR
according to the invention;
FIG. 3 is a top view of an HVR according to the
invention;
FIG. 4 is a perspective view of the hardened
memory subassembly with the beacon bracket removed;
FIG. 5 is a perspective view of the mounting
base subassembly;
6
CA 02361796 2001-11-09
' r
FIG. 6 is a side elevation view of the hardened
memory subassembly with the beacon bracket removed;
FIG. 7 is a sectional view taken along line A-A
in FIG. G;
FIG. 8 is a sectional detail of the encircled
area of FIG. 2;
FIG. 9 is a side elevation view of the mounting
base subassembly;
FIG. 10 is a sectional view taken along line
IS B-B of FIG. 9;
FIG. 11 is a plan view of the mounting base
subassembly;
FIG. lla is a perspective view of a stacked
memory boards including memory interface converter chips;
FIG. 12 is a sample "screen shot" of the HVR
"home page";
FIG. 13 is a sample screen shot of the HVR
login page;
7
CA 02361796 2004-O1-22
FIG. 14 is a sample screen shot of the HVR
network setup page; and
FIG. 15 is a sample screen shot of the HVR
device update page.
DETAILED DESCRIPTION
Turning now to Figures 1-3, the Hardened Voyage
Recorder (HVR) 10 according to the invention includes two
separable subassemblies. The first subassembly 12 is a
mounting base subassembly designed to be directly
fastened to the ship and provide a watertight cable entry
for power and data connections. The second subassembly
14 is a removable hardened memory subassembly which is
attached to the mounting base with a quick releasing
clamp.
Referring now to the mechanical features of the
subassembly 12, as shown in Figures 1-3, the mounting
base subassembly 12 has a lower flange 16 defining three
mounting holes 18, 20, 22. Two cable connectors 24, 26
are provided for a watertight coupling of power and data
cables (not shown). As seen best in Figures 2 and 8-10,
the subassembly 12 is also provided with a lower flange
28 which is used to provide a sealing engagement with the
removable hardened memory subassembly 14. As seen best
in Figure 8, the upper flange 28 is provided with two
8
CA 02361796 2001-11-09
concentric grooves 30, 32 which are adapted to receive
gasket 34 and o-ring 36. 36 is preferably a rubber
o-ring for moisture protection. 34 is preferably a wire
mesh for EMI protection.
The mechanical features of the hardened memory
subassembly 14 include a bracket 38 for an externally
mounted underwater location beacon 40. The beacon is
preferably provided with dual activation moisture sensors
to avoid inadvertent activation due to spray, rain, or
hosing off. The subassembly 14 also has two lifting
handles 42, 44 and an upper flange 46 which is used to
provide a sealing engagement with the subassembly 12 as
seen best in Figures 2 and 8.
As shown in Figure 1, the HVR also includes a
V-band 48 having two quick release clamps 50, 52. As
mentioned above, the HVR is preferably painted a highly
visible florescent orange with white reflective labels,
e.g. label 54 shown in Figures 1 and 2. The reflective
labels contain the required (by IEC 61996) text: VOYAGE
DATA RECORDER, DO NOT OPEN, REPORT TO AUTHORITIES. A
strip of reflective tape, 19, is shown in FIG. 1, further
satisfying the requirements of IEC 61996.
The presently preferred embodiment of the HVR
10 is approximately thirteen inches high and has a
diameter of approximately eight inches. The lower flange
16 of the subassembly 12 is substantially triangular and
9
CA 02361796 2004-O1-22
is approximately ten inches per side. The total weight
of the HVR is approximately forty one pounds with the
base 12 weighing approximately thirteen pounds and the
memory subassembly 14 weighing approximately twenty eight
pounds.
Before turning to the electronic and software
specifications of the subassembly 12, it should be noted
that the subassembly 14 includes memory 56 which is
protected in a "boiler" 58 such as that disclosed in
Canadian Patent Application No. 2,361,797.
According to the presently preferred
embodiment, electronic access to the memory 56 is
provided by a ribbon cable 60 having a (preferably J10)
connector 62. The memory is preferably a stacked memory
such as that disclosed in Canadian Patent Application No.
2,361,797 or in U.S. Patent Number 5,969,953. More
particularly, the memory is preferably of the type
utilizing "BGA" packaging (ball grid array packages) as
memory components.
Referring now to Figures 5 and 9-11, the
mounting base subassembly 12 includes electronics
(partially shown as 64 and 66 in Figures 9 and 10) for
receiving data and writing data to the memory in the
CA 02361796 2001-11-09
hardened memory subassembly 14.
According to the presently preferred
embodiment, the power connection is provided by a
terminal strip 68 which accepts either 110/220 VAC or 24
VDC or both. The data connection is an ETHERNET
connection which is provided by either an RJ-45 connector
70 or an optional ETHERNET terminal block 72. The AC and
DC power connections may both be active at the same time.
The AC connection is preferably used during normal
conditions and the DC connection is preferably coupled to
the ship's UPS (uninterrupted power supply). The
maximum power consumption is preferably fifteen watts.
According to the presently preferred
embodiment, the stepped down and bridge rectified AC
feeds the same storage capacitor that is fed through a
diode by the DC, so the higher voltage at the anodes will
provide the operating current. IEC 61996 paragraph 4.5.3
requires a two hour reserve uninterrupted power source
(UPS ) .
When connecting the ship's UPS system to the
HVR, either the AC or DC input may be used. Clearly the
negative terminal of the capacitor and the primary side
of the switching power supply are grounded to the DC
return. If AC is the only power wired, a 1K Ohm resistor
ties this input ground to the AC safety ground. The
primaries of the AC input transformer can be strapped in
CA 02361796 2001-11-09
parallel for 115 Vrms or in series for 230 Vrms by means
of jumpers on the terminal board (not shown).
The memory is operated by the DC power from the
secondary of the switching transformer, and is isolated
from the AC and DC power lines. A secondary ground,
which is connected to the case and the ETHERNET shield,
must be tied to the hull to prevent voltage difference
that could induce corrosion. As shown in FIG. 11,
according to a preferred embodiment of the invention, a
ground pad 74 is used for grounding. A notch 76 in the
upper flange 28 of the subassembly 12 is used to prevent
pressure differential in a deep sea pressure environment.
Those skilled in the art will appreciate that
the ETHERNET cabling should be shielded to protect it
from the expected intense RF fields generated by other
shipboard equipment such as radar. The foil shield
should end as close as possible to the case after it has
passed through the sealing connector 26. The shield's
drain wire connects to the ground pad 74 which is located
about one inch from the connector 26. Keeping the shield
as short as possible inside the case prevents it from re-
radiating externally induced signals by using the case as
a voltage node. The drain wire at the other end of the
ETHERNET cable (at the DMU) should also be grounded to
the ship's hull.
12
CA 02361796 2004-O1-22
As mentioned above, according to the presently
preferred embodiment, the memory used in the subassembly
14 is BGA memory. Accordingly, the circuits in the
subassembly 14 include one or more MICs (memory interface
converter chips) needed to interface (convert between)
parallel communications which BGA chips employ and the
serial communications path with processor. The MICs need
to be able to drive the two or more of BGA chips
distributed in the preferred stacked memory. The MICs
may be located on the circuit board 1101 shown in Figure
11a (MIC chips 1102 and 1103) and/or may be distributed
among the memory circuit boards shown in Figure 11a. The
processor communicates with the MICs to address memory
and the MICs determine which board or stack contains the
addressed memory.
Further, as mentioned above, according to the
presently preferred embodiment, the HVR receives data via
TCP/IP (terminal connection protocol/internet protocol)
over ETHERNET. The HVR is therefore assigned an IP
address and is configurable via a "web browser". This
also enables the formation of a network of multiple HVRs
all coupled to numerous sensors via the ETHERNET network.
Figures 12-15 illustrate a sample interface to
the HVR accessible with any web browser coupled to the
ETHERNET network to which the HVR is coupled. Those
skilled in the art will appreciate that the ship's
13
CA 02361796 2001-11-09
ETHERNET network could be connected to the Internet via a
satellite link, thus making the HVR available from
anywhere in the world.
Figure 12 shows a sample HVR homepage. The
default URL of the homepage is 192.168Ø2 which is pre-
set at the factory but which can be changed as shown in
Figure 14. The homepage Main Menu, provides the main
entry point to HVR system configuration setup via a web
browser and provides the links for the configuration
options. In addition links are available that describe
the HVR Interface Details, HVR System Maintenance, and
HVR System Information.
The "Network Setup" link shown in Figure 12
links to the web page shown in Figure 14 providing a
network hostname and IP address setup data entry form.
The "Flash Setup" link shown in Figure 12 links
to a web page shown in Figure 15 providing a memory
partition setup data entry form.
The "Sys Maintenance" link shown in Figure 12
links to a web page (not shown) listing the existing
Flash Memory Setup.
The "Sys Information" link shown in Figure 12
links to a web page (not shown) providing specific HVR
software and IP address information.
14
CA 02361796 2001-11-09
The "Set Password" link shown in Figure 12
links to a web page (not shown) providing a password
setup data entry form.
S
The "HVR Interface" link shown in Figure 12
links to a web page (not shown) providing HVR system
interface information.
The main menu shown in Figure 12 can be
accessed without entering a password, but in order to
change any HVR system configurations, a password is
required to be entered via the password entry page shown
in Figure 13. In particular, a password is required to
access the Network Setup, Flash Setup, and Set Password
pages. Access to any of these pages times out when idle
for 300 seconds (which is configurable as shown in Figure
14) and a password must be re-entered to continue with
HVR setup modifications.
The Login Screen of Figure 13 will appear no
matter which system configuration button is selected
first.
The HVR is shipped from the factory with the
following default IP settings:
IP address: 192.168Ø2
Subnet Mask: 255.255.255.0
Default Gateway IP: 192.168Ø1
IS
CA 02361796 2001-11-09
Those skilled in the art will appreciate that
these are the default settings commonly used with "web-
accessible" devices. The "192.1G8.x.x" IP address scheme
is part of a "reserved" block of addresses intended
S strictly for networks that are not connected to the
Internet. When using addresses of this type, the host
computer must be configured to an address in this range
in order to "see" the HVR and access the HVR's Web pages.
By selecting the Network Setup link in Figure
12, the user is taken to the page shown in Figure 13
requiring a password entry. The default password for the
HVR is "L3HVR". Upon entering the correct password, the
user will be taken to the page shown in Figure 14 where
the network parameters can be set as required. Changes
made will not take effect until the HVR is powered down
and back up. Once the settings have been made, the HVR
can be connected to the VDR network where it should
respond at the configured IP address.
Using the page shown in Figure 15, the user can
modify or set up the memory areas used for data storage
on the HVR. Each of these areas or partitions require
that two parameters be specified: the partition size and
the partition name. This page shows the number of
currently available memory devices as well as the per
device size in Kilobytes. The user partitions and
allocates the HVR memory data storage from the available
device pool. The configuration of the memory areas
16
CA 02361796 2001-11-09
requires that the user specify the size of each memory
partition in device units, expressed as the number of
devices to be allocated to that memory area. The
partition size is thus the device size multiplied by the
S number of devices.
The HVR system internally allocates devices
from its internal free pool of devices in order to fill
the request. The partition configuration request is
processed starting with partition 0 (ZERO) and proceeding
to partition 9 (NINE). The partition allocations cannot
exceed the number of available devices. Partition
allocations are processed until all available devices
have been allocated.
The partition name is required during the
actual recording of data into a partition. The
partition/stream name is to be used by the client
application wishing to establish a data connection to the
HVR for the storage of data to a particular partition.
The connection set up for a data stream requires the
partition name. The VDR must use the same partition
(stream) name established during the HVR memory
configuration in order to establish communication with
that partition (stream).
17
CA 02361796 2001-11-09
Once the HVR has been configured, it appears to
the outside world as a smart interface to a "pool" of
nonvolatile memory. Application programs running on one
S or more data acquisition systems coupled to the ship's
network can utilize the pre-allocated memory partitions
for storage and retrieval purposes. Each stream
partition is treated as a virtual storage loop in which
new data continuously overwrites the oldest data in the
partition. The HVR processor keeps track of the current
write location in the virtual loop for each partition and
preserves this through power cycles in nonvolatile
storage.
In order to store data in a previously
allocated partition, or retrieve data from such a
partition, software on the client acquisition system must
"open" a TCP/IP Socket Connection to the Data Acquisition
Server in the HVR. This Server accepts Socket
Connections at Port 5000 of the IP Address assigned to
the HVR. Once a connection has been made to the HVR Data
Acquisition Server, the acquisition software sends a
command which identifies the target partition and the
requested operation. The partition is identified by
using the name that was specified for the stream during
the configuration of the memory pool.
18
CA 02361796 2001-11-09
The partition stream can be opened for read or
write access, or to request "write status" information.
Once the socket connection has been established, and the
S appropriate command issued, data is sent or received over
the Socket Connection. The HVR Data Acquisition Server
will accept simultaneous socket connections from multiple
client processes as well as multiple socket connections
from a single client process. This automatically results
from the Client-Server model of the "Berkely Software
. Distribution" socket interface that is used by the HVR.
There are, however, some limitations imposed by the HVR
software itself.
IS Specifically, there can be only one active
"Write" client connection associated with a particular
Stream Partition. The HVR does, however, support
simultaneous reading from Partitions while writing. The
"status query" is supported on a Stream regardless of
whether or not there is an active "Read" or "Write"
connection on that partition.
The application layer above TCP/IP is the
functional interface between a client data acquisition
subsystem and the HVR. It is assumed that the lower
protocol layers ensure error-free and timely delivery of
messages in both directions. Furthermore, an ETHERNET
HVR interface cnith TCP/IP layers does not rule out
multiple concurrent Users of the HVR. Bandwidth of the
19
CA 02361796 2001-11-09
storage media and communications channels are, of course,
issues which must be considered at the system level.
All messages sent to the HVR begin with a
single byte message length value. This represents the
number of bytes (characters) in the remainder of the
message. For.example, the message for opening a
partition named "VDR-Radar" for writing would consist of
a byte value of OxOB (11 characters in the remainder of
the message), followed by the ASCII characters:
WVDR Radar, followed by a Null terminator (byte value
0x00). Note that the Partition Name, "VDR Radar" is a
9--character ASCII sequence which is to be followed by a
Null terminator character. Along with the 'W' character
(for writing) that precedes the Partition Name, the total
length of the message is 11 characters. There should be
no additional spaces within the message. The "count" byte
can be thought of as a specification of exactly how many
more characters will be following in order to complete
the message. Since the "count" specification is a single
byte, the maximum message length is 255 characters.
Certain HVR messages can include one or more
optional arguments. In all cases the optional arguments
follow the Null terminator of the base message string.
Each argument is, itself, a Null--terminated ASCII
string. Numerical values contained in optional arguments
are ASCII decimal strings. An example of an optional
argument which includes a decimal value would be one
CA 02361796 2001-11-09
which limits the amount of data to be sent by the HVR in
response to the "Read from Stream" command.
In this case, the added argument might be the
S string "X25". The 'X' character indicates that this is
the "Xfer Count" (transfer count) argument, and the "25"
is a two--character ASCII--decimal value which represents
25 Mbytes. The "X25" string represents four additional
bytes of the complete command (there must be a Null
terminator), and would be so reflected in the message
length byte that precedes the base message string. It is
essential that the base message string, and each optional
argument string be followed by a Null terminator byte.
There are some optional arguments that consist of a
single ASCII character, and these too must be followed by
the Null terminator byte.
Since the message length byte that precedes a
request message tells the HVR exactly how many additional
bytes must be consumed from the Socket stream in order to
obtain the request, that byte must reflect all of the
strings and their associated Null terminators. Otherwise
the HVR will not "consume" the entire message before
attempting to interpret it.
The "Write to Stream" command is sent by the
acquisition system as the first data on a successfully
opened TCP/IP Socket Connection. This command consists
of an upper or lower--case 'w', followed by the Stream
21
CA 02361796 2001-11-09
Name that was specified when the stream partition was
allocated, followed by a zero value to terminate the
Stream Name string. Note that the command must be
preceded by the "count byte" as described above.
S
If the HVR processor finds this to be a valid
Stream Name, it will reply with a single character
response of 'G'. If there is a problem with the attempt
to establish the "write" connection, one of several error
responses will be sent. Once the acquisition client has
received a 'G' response, it can begin to send data on the
open socket connection stream.
Optional arguments for the "Write to Stream"
1S command are: "N", for "No Wrap " mode, and "R" for "Reset
Write Indices". Neither option takes any additional
parameters.
The "No Wrap" option causes the HVR to first
reset the Write location to the start of the Partition
before beginning to store any data, and also to stop
writing to the specified Stream when the end of the
Partition is reached. This is primarily useful in
testing the integrity of a Partition.
2S
The "Reset Indices" option causes the Write
location to be reset to the start of the Partition before
beginning to store any data. This does, however, allow
writing to "Wrap" when the end of the Partition is
CA 02361796 2001-11-09
reached. This is also intended as a "test" feature.
The " Read from Stream" command is sent by the
acquisition system as the first data on a successfully
S opened TCP/IP Socket Connection. This command consists
of an upper or lower case 'r', followed by the Stream
Name that was specified when the stream partition was
allocated, followed by a zero value to terminate the
Stream Name string. Note that the command must be
preceded by the "count byte" as described above.
If the HVR processor finds this to be a valid
Stream Name, it will reply with a single character
response of 'G'. If there is a problem with the attempt
to establish the "read" connection, one of several error
responses will be sent. Once the acquisition client has
received a 'G' response, it can begin to read data from
the open socket connection stream.
Optional arguments .for the "Read from Stream"
command are: "N", for "No Wrap" mode, "O" for specifying
an "Offset" in Mbytes at which the Reading should begin,
and "X" for specifying the total number of Mbytes to be
sent by the HVR.
The "N" option is the counterpart of the "No
Wrap" option that is available on the "Write to Stream"
command. This option causes the HVR to begin reading at
the top of the Partition, and stop reading when the end
23
CA 02361796 2001-11-09
of the Partition is reached. This is typically used to
verify the content of a partition that was filled, for
test purposes, using the "N" option on the "Write to
Stream" operation.
The "O"" and "X" options are similar in that
they are both followed by an ASCII-decimal value that
represents a number in Mbytes. The "O" option represents
a backwards offset, relative to the current Write
location, at which the reading of data from the Partition
is to begin. This is a positive value expressed in
Mbytes.
For example, an argument of "015" would back up
by 15 Mbytes from the current Write location. That is,
it would set the Read pointer back at the data that was
stored 15 Mbytes ago. There are some constraints
associated with this option. For example, if a value is
specified which is larger than the Partition storage
area, then the Read location remains at the current Write
location. Also, if the Partition has not been "filled"
since the last time the Write location was reset, then
the offset will not be adjusted backwards beyond the top
of the Partition. This is because data which "follows"
the current Write location is meaningless.
24
CA 02361796 2001-11-09
The "Status Query on Stream" command is sent by
the acquisition system as the first data on a
successfully opened TCP/IP Socket Connection. This
S command consists of an upper or lower case 's', followed
by the Stream Name that was specified when the stream
partition was allocated, followed by a zero value to
terminate the Stream Name string. Note that the command
must be preceded by the "count byte" as described above.
If the HVR processor finds this to be a valid
Stream Name, it will reply with a single character
response of 'G'. If there is a problem with the attempt
to establish the "status query" connection, one of
several error responses will be sent. If the 'G'
response is received, it will be followed by a "Status
Response" message which conforms to the message format
described for commands to the HVR. That is, the
remainder of the response will consist of a "count byte"
followed by a Null terminated string. The string will be
of the form: " L:n T:n".
Note that the quotes are NOT part of the
response, but are shown to emphasize that the entire
response is an ASCII, Null terminated string. The letter
'n' indicates an ASCII decimal representation of the
appropriate error count. The first 'n' value is the
"Loop Error Count" and represents the number of write
errors that occurred on the current pass through the
?~
CA 02361796 2001-11-09
Stream Partition.
This value is cleared automatically at the
start of each pass through the Partition's memory loop.
The second 'n' represents the "Total Error Count", and is
the accumulated number of errors since the counters were
last cleared (manually or as a result of setting up the
Partition Map).
The response to the 'W', 'R', or 'S' commands
is a single ASCII character. There is no "count byte" or
Null terminator.
If the Partition Name is valid and access has
been established, the response is a 'G' character. If
the Partition Name is not recognized, the response is an
'S! character. If the Partition has no devices allocated
to it, the response is an 'E' character. If the
Partition is busy (another client is already writing in
the Partition), the response is a 'B' character. If the
Partition is Out of Service for some other reason (failed
devices, etc.), the response is an 'O' character.
Note that the response to the 'S' command is
somewhat unique in that it follows the "single ASCII
character" form, but if a valid request was made,
continues with a "full message" type of response.
2G
CA 02361796 2001-11-09
The HVR allows only~one Client to be writing to
a particular Partition at a time. That is, only one 'W'
connection will be allowed for each in-service Partition.
The HVR will also accept one or more 'R' connections for
a Partition, even if there is currently an active 'W'
connection. Issues related to the effects of multiple
connections on performance (system throughput) must be
carefully considered.
The response to a 'W' command, for a Partition
that already has an active 'W' connection, is the 'B'
message (busy).
IS The current implementation of the HVR subsystem
is capable of data transfer to or from the protected
memory store at a rate of around 1.5 Mbits per second
(using 10-Base T ETHERNET). That is, a data acquisition
host or hosts can send data to the protected memory
store, or retrieve data from the store, at approximately
this rate, when all other conditions are optimal.
When sending data to the HVR, the maximum rate
can only be achieved if at least three partitions are
being written to concurrently. This is a consequence of
the architecture of the memory devices being used in the
protected memory store and the HVR software that manages
the devices. That is, the maximum write rate relies on
the HVR software being able to continuously manage
27
CA 02361796 2001-11-09
concurrent writes in multiple devices.
There are essentially two buffers used to
process the data. The first is the receipt of data
packets into an incoming queue, the throughput of this
process is approximately 1.5 Mbits per second. The
second is in the processing of those data packets from
the incoming queue to the flash devices, the throughput
of this process is dependent on how the flash chips are
managed/mapped. A write to a flash device is slow,-
relatively speaking, and the software must wait for a
write to complete on a given chip before another write
can begin. Therefore, if there is only one partition,
the writes are all sequential and the throughput will
slow to the rate of the chip write function (which can be
chip and temperature dependent).
If however, there are multiple partitions,
concurrent writes can occur because the software will be
writing to different chips. This effectively increases
the throughput by n times, where n is defined by the
number of partitions. Since the throughput of the
process to receive incoming data packets is approximately
1.5 Mbits per second, the goal of the host computer is to
partition the flash devices so that this rate can be
achieved. Experimentation has shown at least three to
four partitions are required.
CA 02361796 2001-11-09
The maximum read rate is also around 1.5 Mbits
per second, assuming that there is no simultaneous
writing. The rate of a chip read function is much faster
than the write so even if there is only one read
occurring (sequential access to a chip) it can keep up
with the rate of the process to receive incoming data
packets.
When reading and writing are performed
together, the available bandwidth of the HVR will be
distributed between the operations in a manner that will
vary depending on system dynamics.
There have been described and illustrated
herein a hardened voyage data recorder and an example of
software for using the recorder over an ETHERNET network.
While particular embodiments of the invention have been
described, it is not intended that the invention. be
limited thereto, as it is intended that the invention be
as broad in scope as the art will allow and that the
specification be read likewise. In particular, the
specific arrangement of web pages and the specific
communications protocol described herein represent a
presently preferred embodiment, but the invention is not
limited thereto.
29
CA 02361796 2001-11-09
It will therefore be appreciated by those
skilled in the art that yet other modifications could be
made to the provided invention without deviating from its
spirit and scope as so claimed.
_p 0
