Omron NT31 Operation Manuals page 461

Inputting Character Strings
Recording Format for the Alarm History Record
Reference
Maximum Number of Records
Checking the Record
450
For the alarm history record, the following data is recorded in the memory for bit
memory tables allocated to bits whose status changes to "1" (ON).
- Message (contents of a character string memory table set for the bit memory
table)
- Time of display
- The alarm history record data is backed up by the built-in battery of the
NT31/NT31C and is therefore retained even when the power to the
NT31/NT31C is turned OFF or the NT31/NT31C is reset.
- Bit 1 (alarm history initialization) of the PT status control bits can also be used to
initialize the alarm history.
S Occurrence order
The data of up to 256 bit memory tables (bits) can be recorded in the occurrence
order alarm history record. The operation when 256 records is exceeded de-
pends on the setting made for "Alarm (Use Ring Buffer)" on the "PT Configura-
tion" – "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.
S Frequency order
The data of up to 255 screens can be recorded in the frequency order alarm his-
tory record. Even if this limit is exceeded, still 255 records remain displayed.
There are two methods for checking the alarm history record: checking the record
contents in the Maintenance mode of the NT31/NT31C, 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.
S Displayed data
The data displayed with the alarm history record function are described below.
- Occurrence order
The records are displayed in the order in which the status of the set bit memory
tables (bits) changed to "1" (ON). Whether the records are displayed from the
oldest first or from the newest first is set with the memory switches at the
NT31/NT31C.
- Frequency order
The records are displayed in the order of the number of times the statuses of
the bit memory tables have changed to "1" (ON).
Section 7-15