| The trend history system has a master file
for each trend. This master file manages the trend history data
files. When a history file is filled, data will be written to
another trend data file (pointed to by the master file).
Master File Structure
The master file (.HST) has a header followed by an array of
history file information. The history files are ordered so that the
most recent one is at the top.
| MASTERHDR |
| HISTFILE most recent |
| HISTFILE |
| HISTFILE oldest |
|
|
MASTERHDR structure
| NAME
|
SIZE
|
DESCRIPTION
|
| title |
128 |
Title of the file (ASCII). It contains
information, such as file version, type, start time and logging
name. |
| ID |
8 |
ID for Citect files. It is set to
"CITECT". |
| type |
2 |
Type of the Citect file. It is set to
0, which is FILE_TYPE_TREND. |
| version |
2 |
Version number of the trends. (3 or 4
depending on the storage method of the Trend) |
| alignment |
4 |
alignment for 16 bytes |
| Mode |
4 |
Indicates the mode of the MASTER file.
(For future use. Currently it is set to 0.) |
| History |
2 |
Maximum Number of history files to be
created. (not including AddOn) |
| nFiles |
2 |
Number of history files currently
created. (not including AddOn) |
| next |
2 |
Next history file number. Internal use
only, users MUST NOT use this entry to get the next history
file. |
| AddOn |
2 |
Shows the number of history files
added onto the system through user functions. User can add old
(backed up) history files to the system temporarily by using
TrnAddHistory() and TrnDelHistory(). |
| alignment |
20 |
alignment for 16 bytes |
NOTE 1: You have to read the whole master file to determine the
sequence of history files.
Parts of the HISTFILE structure and Trend Data File are
different, depending on the storage method. So here are the
structures for the different Storage Methods.
Scaled (2-Byte samples) Storage Method
HISTFILE structure
| NAME
|
SIZE
|
DESCRIPTION
|
| Name |
144 |
History file name. |
| BinHdr |
96 |
History file binary header. See
HISTBINHDR structure. |
HISTBINHDR structure
| NAME
|
SIZE
|
DESCRIPTION
|
| ID |
8 |
ID for Citect files. It is set to
"CITECT". |
| type |
2 |
Type of the Citect file. It is set to
0, which is FILE_TYPE_TREND. |
| version |
2 |
Version number of the trends. (equal
to 3 for this Storage Method) |
| StartEvNo |
4 |
Starting Number for events in this
history file. (Event Trends only.) |
| LogName |
32 |
Name of the trend record that owns the
history file. |
| Mode |
4 |
Indicates the mode of the history
file. (For future use. Currently it is set to 0.) |
| Area |
2 |
The area that has access to the
acquired data. |
| Priv |
2 |
The access rights required to execute
the command. |
| FileType |
2 |
History File Type. Set to 0 for
Periodic and Periodic_Event Trends. Set to 4 for Event Trends. |
| SamplePeriod |
4 |
Sample period of logging (in
milliseconds) |
| sEngUnits |
8 |
Units of scales. (Set to the units of
the trend record.) |
| Format |
4 |
Format of scales. (Set to the format
of the trend record.) |
| StartTime |
4 |
The earliest time that a sample can
have and be placed in this file, in seconds since 1970. |
| EndTime |
4 |
For Periodic Trends the EndTime is
always set to the latest possible sample time that can be put into
this file. For Event Trends the EndTime is the time of the newest
sample stored in the file (one less than the StartTime if there are
no samples in the file). Stored as a number of seconds since
1970. |
| DataLength |
4 |
Shows the number of data items.
DataLength = (File Size - HeaderSize) / 2 |
| FilePointer |
4 |
The location of the newest sample in
the file, in number of samples from the start of the data portion
of the file.(Periodic Trends only). |
| EndEvNo |
4 |
The event number of the next sample
after the last one in this file. (Event Trends only) |
| alignment |
2 |
for 16 bytes |
Trend Data File structure - Periodic and Event Periodic
Trends
HISTFILEHDR
data (2 bytes per data)
Trend Data File structure - Event Trends
HISTFILEHDR
data (SCALEDEVENTSAMPLE per sample)
SCALEDEVENTSAMPLE structure
| Value |
4 |
The value of the sample |
| Time |
4 |
The time of the sample in seconds
since 1970 |
| Milliseconds |
4 |
The milliseconds of the time of the
sample |
HISTFILEHDR structure
| title |
112 |
ASCII title of the file. It contains
information, such as, file version, type, start time and logging
name. |
| DefScale |
16 |
default scales. See the structure of
DEFAULTSCALES below. |
| BinHdr |
96 |
Binary header for history files. See
HISTBINHDR structure |
|
|
|
|
DEFAULTSCALES structure
| RawZero |
4 (float) |
| RawFull |
4 (float) |
| EngZero |
4 (float) |
| EngFull |
4 (float) |
Floating Point (8-Byte samples) Storage Method
HISTFILE structure
| NAME
|
SIZE
|
DESCRIPTION
|
| Name |
272 |
History file name. |
| BinHdr |
160 |
History file binary header. See
HISTBINHDR structure. |
HISTBINHDR structure
| NAME
|
SIZE
|
DESCRIPTION
|
| ID |
8 |
ID for Citect files. It is set to
"CITECT". |
| type |
2 |
Type of the Citect file. It is set to
0, which is FILE_TYPE_TREND. |
| version |
2 |
Version number of the trends. (equal
to 4 for this Storage Method) |
| StartEvNo |
8 |
Starting Number for events in this
history file. (Event Trends only.) |
| alignment_1 |
12 |
for 16 bytes |
| LogName |
64 |
Name of the trend record that owns the
history file. |
| Mode |
4 |
Indicates the mode of the history
file. (For future use. Currently it is set to 0.) |
| Area |
2 |
The area that has access to the
acquired data. |
| Priv |
2 |
The access rights required to execute
the command. |
| FileType |
2 |
History File Type. Set to 0 for
Periodic and Periodic_Event Trends. Set to 4 for Event Trends. |
| SamplePeriod |
4 |
Sample period of logging (in
milliseconds) |
| sEngUnits |
8 |
Units of scales. (Set to the units of
the trend record.) |
| Format |
4 |
Format of scales. (Set to the format
of the trend record.) |
| StartTime |
8 |
The earliest time that a sample can
have and be placed in this file. (in number of 100 nanosecond time
units since 1st of January, 1601) |
| EndTime |
8 |
For Periodic Trends the EndTime is
always set to the latest possible sample time that can be put into
this file. For Event Trends the EndTime is the time of the newest
sample stored in the file (one less than the StartTime if there are
no samples in the file). (in number of 100 nanosecond time units
since 1st of January, 1601) |
| DataLength |
4 |
Shows the number of data items.
DataLength = (File Size - HeaderSize) / 8 |
| FilePointer |
4 |
The location of the newest sample in
the file, in number of samples from the start of the data portion
of the file.(Periodic Trends only). |
| EndEvNo |
8 |
The event number of the next sample
after the last one in this file. (Event Trends only) |
| alignment_2 |
6 |
for 16 bytes |
Trend Data File structure - Periodic and Event Periodic
Trends
HISTFILEHDR
data (8 bytes per data)
Trend Data File structure - Event Trends
HISTFILEHDR
data (FLOATEVENTSAMPLE per sample)
FLOATEVENTSAMPLE structure
| Value |
8 |
The value of the sample |
| Time |
8 |
The time of the sample (in number of
100 nanosecond time units since 1st January, 1601) |
HISTFILEHDR structure
| title |
112 |
ASCII title of the file. It contains
information, such as, file version, type, start time and logging
name. |
| DefScale |
16 |
default scales. See the structure of
DEFAULTSCALES below. |
| BinHdr |
160 |
Binary header for history files. See
HISTBINHDR structure |
DEFAULTSCALES structure
| RawZero |
4 (float) |
| RawFull |
4 (float) |
| EngZero |
4 (float) |
| EngFull |
4 (float) |
|
