Omron NT21 Reference Manual page 263

Special Functions
Recording Format for the
Alarm History Record
Reference:
Maximum Number of Records
Checking the Record
sible to specify character string memory table entries that contain messages
indicating the contents of alarms.
Only bits for which the History attribute is set are objects of the alarm history
record function. Bits for which History is set are continually monitored during
operation of the PT regardless of the screen being displayed.
2. Initializing the Alarm History
Before recording can be started, the alarm history must be initialized from
the System Menu of the PT to clear the past records.
3. Recording the Alarm History
Operate the PT as usual.
When the status of a bit for which History is set changes to 1 during opera-
tion, the time of this event and the number of times the bit has come ON are
recorded.
4. Checking the Alarm History Record
Display and check the recorded alarm history record.
There are two methods for doing this: displaying the record from the System
Menu, and displaying a screen for which an alarm history element is regis-
tered during operation.
In either case, the records can be presented in occurrence order (order of
display) or frequency order (order of frequency of display).
For the alarm history record, the following data is recorded in the memory for bit
memory table entry for which the status of the allocated bits changes to 1 (ON).
Message (contents of a character string memory table entry set for the bit
memory table entry)
Time of display
S The alarm history record data is backed up by the battery in the PT and is
therefore retained even when the power to the PT is turned OFF or the PT is
reset. (The Battery is an option for the NT21.) If the Battery is not being used,
the alarm history record data will be cleared when the power supply to the PT
is turned OFF or the PT is reset.
S Bit 1 (alarm history initialization) of the PT status control bits can also be used
to initialize the alarm history.
Occurrence order
The data of up to 256 bit memory table entries (bits) can be recorded in the
occurrence order alarm history record. The operation when 256 records is
exceeded depends on the setting made for Alarm (Use Ring Buffer) on the
PT Configuration – System screen at the Support Tool: select whether the
record is to be stopped or the older records are to be deleted.
If no check mark is set for Alarm (Use Ring Buffer), recording is stopped, and
if a check mark is set, the old records are progressively deleted.
Frequency order
The data of up to 255 screens/bit memory table entries can be recorded in
the frequency order alarm history record. Even if this limit is exceeded, still
255 records remain displayed.
There are two methods for checking the alarm history record: checking the re-
cord contents in the Maintenance mode of the PT, and displaying a screen for
which an alarm history element is registered during operation.
The display for the alarm history record function differs depending on whether it
was called from the Maintenance mode or during operation.
Section 2-16
247