Omron NT31C Reference Manual page 192

Alarm List, Alarm History
• [When a message is added]
• If a message is added outside the display range (before or after the display
range), there is no change in the messages being displayed.
• If a message is added within the display range, the new message is dis-
played, and the messages following it are shifted one line downward.
• [When a message is deleted]
• If a message is deleted outside the display range (before or after the dis-
play range), there is no change in the messages being displayed.
• If a message is deleted within the display range, the messages following it
are shifted one line upward, except when it is the topmost message in the
display that is deleted, in which case the message immediately preceding
the present display range is displayed in its place.
If all the displayed messages are deleted at the same time, messages are
displayed starting with a message with the same serial number (counting
from the top) as the topmost of those that were displayed. (For example, if
the previous display started from serial number 7, the new display will also
start from a message with serial number 7.)
Alarm History in Occurrence Order
With an alarm history in occurrence order, when the status of the monitored host
bit changes to 1 (ON), the corresponding message becomes the latest message
(the messages are displayed from the oldest first or from the newest first, de-
pending on the memory switch setting made at the PT). When the status of the
bit changes back to 0 (OFF), the message remains displayed.
If the statuses of multiple bits change to 1 (ON) at the same time, the bit memory
table with the smallest bit memory table number is given priority.
• [Display from oldest record first]
Since new messages are added at the end of the history, the displayed mes-
sages do not change. However, when the final page is displayed and a mes-
sage is added below it, the
inform the operator that a message has been added.
• [Display from the newest record first]
New messages are added at the top of the history. When a message is add-
ed, the screen will switch to the display starting from the first message re-
gardless of the current display position.
Alarm History in Frequency Order
With an alarm history in frequency order, when the status of a monitored host bit
changes to 1 (ON), the number of times that bit has changed to 1 (ON) is deter-
mined and the display is changed to reflect the new descending order of fre-
quency of occurrence. When the bit status changes back to 0 (OFF), its frequen-
cy display remains unchanged.
If there are bits with the same frequency of occurrence, the one whose bit
memory table has the smallest bit memory table number is displayed closest to
the top of the history.
The display contents change in real time according to the frequencies of oc-
currence, but the display range does not change. The serial number (count-
ing from the top) of the message at the topmost position is retained until the
display range is changed by touch switch operation.
Lighting of The Message Display Field and Touch Switches for Scrolling
The message display field and touch switches for scrolling light as follows ac-
cording to the alarm list/history status.
Message Display Field
When a message field is pressed for the first time after it is displayed, or pressed
after another message has been pressed, if image/library data is set for the cor-
touch switch is displayed in reverse video to
Section 2-11
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